Office chair gas cylinder replacement
Two problems, one part. If your chair sinks, the cylinder has failed. If it will not go high enough, a longer cylinder fixes what no adjustment can.
By Sawyer V. · Published October 10, 2026
We earn a commission if you buy through the links on this page, at no extra cost to you. It does not affect the order of the picks - the rubric does that, and here is how we are funded. Prices were last verified October 11, 2026.
What we did and did not do
Units we claim to have tested: 0. Everyone in this category says they tested twenty chairs. We have not sat in any of these, and we say so.
What we did instead: compiled every figure each manufacturer publishes, computed the fit ranges from a cited anthropometric table, and linked the source for each number so you can check the arithmetic. Where a manufacturer does not publish a figure, we say that rather than filling the gap. The full method, including what we cannot assess, is here.
If your chair sinks while you sit in it, the gas cylinder has failed and a replacement costs about twenty-five dollars. Nothing else on the chair is wrong. The pick is the MASTERY MART 5.5 in stroke: 11.69 in compressed, 17.2 in extended, 1000 lb, Class 4, stated to BIFMA/ANSI - the most complete spec sheet in the field and the size that suits an ordinary task chair.
If your chair will not go HIGH enough, a longer cylinder is the only fix there is - and it is the cheapest thing on this entire site. The MASTERY MART 8 in stroke extends to 21.85 in and its maker says in as many words that it is for "tall users over 6'2", drafting chairs, bar stools, and standing desk chairs". That turns a task chair into something that reaches a counter, for $37.99 instead of a new chair.
One warning before you buy on stroke alone: a longer cylinder raises your chair's FLOOR as well as its ceiling. The 8 in version is 13.97 in compressed against the 4 in version's 9.88 in - so its lowest seat position is four inches higher. At a standard 29 in desk that is the opposite of what you want. The compressed length is the figure people skip and then regret.
Which problem do you have?
| Symptom | Cause | Fix |
|---|---|---|
| Seat slowly sinks while you sit | Gas seal has failed - the single most common chair failure | Replace the cylinder, like for like on compressed length |
| Seat will not rise at all | Failed cylinder, or the lever/cable is disconnected | Check the lever first; if the lever works, replace the cylinder |
| Seat works but will not go high enough | Nothing is broken - the cylinder is simply too short | Fit a longer-stroke cylinder; this is an upgrade, not a repair |
| Seat wobbles side to side | Base or caster stems, not the cylinder | A cylinder will not fix this |
| Seat tilts forward or back on its own | Tilt mechanism or tension knob | A cylinder will not fix this either |
The three figures that decide fit
Measure the old one before you order anything. Three numbers, and every good listing in this field publishes all three:
- Compressed length - the cylinder at its shortest. This sets your seat's LOWEST position. Match it if you are repairing; go longer only if you want a higher floor as well as a higher ceiling.
- Extended length - the cylinder at its tallest. This sets your seat's highest position.
- Stroke (travel) - extended minus compressed. This is how much adjustment you get, and it is what the listings advertise. 4 in is a normal task chair; 8 in is drafting-chair territory.
The two fit diameters are effectively standard and most listings confirm them: a 2 in (50 mm) outer column that drops into the base, and a 1-1/8 in (28 mm) piston shaft that goes up into the seat plate. Five of the seven here publish both. Two publish neither, which is the one genuine risk of buying the cheapest option.
Every published figure, side by side
| Cylinder | Compressed | Extended | Stroke | Capacity | Class / test |
|---|---|---|---|---|---|
| MASTERY MART 5.5 in (rank 1) | 11.69 in | 17.2 in | 5.5 in | 1000 lb | Class 4, BIFMA/ANSI |
| MASTERY MART 4 in (rank 2) | 9.88 in | 13.6 in | 4 in | 1000 lb | Class 4, BIFMA/ANSI |
| MASTERY MART 8 in (rank 3) | 13.97 in | 21.85 in | 8 in | 1000 lb | Class 4, BIFMA/ANSI |
| Rythalix 6.3 in (rank 4) | - | 18.5 in (range from 12.2) | 6.3 in | 1000 lb | Class 4 |
| Rythalix 3.9 in (rank 5) | - | 14 in (range from 10) | 3.9 in | 1000 lb | Class 4 |
| Ainilaily (rank 6) | 14.3 in | 22.3 in | 8 in range | 450 lb | SGS + LGA |
| Office Oasis kit (rank 7) | - | - | - | - | Class 4 |
Read the bottom row. The Office Oasis kit publishes no length, no stroke and no capacity at all - and it is the most expensive item in the field at $39.95. It is here because it ships the removal tool, which is the part of this job that actually goes wrong, and because the maker states a lifetime warranty against leaking or sinking. If you want the tool, buy it knowingly; if you want a part that reaches a specific height, buy one that tells you its lengths.
What Class 4 means, and what BIFMA has to do with it
"Class 4" is a durability classification for the cylinder itself, and every cylinder in this field claims it. It is the highest of the common classes, so in practice it is table stakes rather than a differentiator - if a listing does NOT say Class 4, that is the signal.
Three of these cite BIFMA/ANSI alongside it. Worth knowing what that does and does not mean: ANSI/BIFMA X5.1 is the office-chair test standard and it is built around a 275 lb occupant; X5.11 covers 253 to 400 lb. A cylinder "manufactured to meet BIFMA/ANSI" is a component claim, not a certification of your assembled chair - your chair's own rating still governs. How capacity ratings actually work.
The 1000 lb figure on five of these is a component load rating and it is not your chair's capacity. A 1000 lb cylinder in a 250 lb chair gives you a 250 lb chair. The base, the seat plate and the casters are all still rated for what they were rated for.
The honest caveats
Removal is the hard part
Fitting a new cylinder is genuinely easy - it drops into the base and the seat sits on the shaft. Getting the old one OUT is the step that defeats people, because the taper is friction-fitted and years of load have set it. Every listing here describes the same method: lay the chair on its side and strike the base ring with a rubber mallet or a hammer. One listing sells a purpose-built removal tool for exactly this reason and says it invented the category in 2016.
We have not done this job on any of these chairs and we are not going to walk you through swinging a hammer at a pressurized gas strut. Two things we will say, because the listings say them: the cylinder is pressurized, and the makers that mention it tell you not to cut, drill or puncture it. If that is not a job you want, this is a thing a furniture repair shop does cheaply.
Check your chair is actually worth it
A $25 part in a chair whose foam is flat and whose mesh has gone slack is $25 spent on the one component that was still working. The cylinder is the right fix when the rest of the chair is sound - which, on a chair whose maker published a five-year warranty, it often is. How long office chairs actually last, and when the cylinder is the wrong fix.
This is the cheapest answer to a fit problem on this whole site
Worth saying loudly because no chair manufacturer will. If a chair's seat depth and backrest suit you but its seat-height ceiling is an inch or two short, a longer cylinder is a $30 fix for a problem that otherwise costs you a whole new chair. Of the 38 task and drafting chairs we have verified, 15 publish a seat-height range at all - so this is also the fix for discovering after purchase that the one you bought tops out too low. How to read the rest of a chair spec sheet.
The cylinders, ranked on published length and stroke
Ranked on the published rubric. Tap a row for the full write-up; the price button goes straight to Amazon. Every figure in the write-ups is the manufacturer's own published specification, linked at the source. We have not sat in any of these.
| # | Product | Best for | Score | Price |
|---|---|---|---|---|
| 1 |  MASTERY MART Chair Gas Cylinder, 5.5 in Stroke Best Overall | 5.5 in of travel, 11.69 in compressed | 9.0 | $31.99 - View on Amazon #ad disclosure · October 11, 2026 |
| 2 |  MASTERY MART Chair Gas Cylinder, 4 in Stroke Best Like-for-Like Swap | A failed cylinder on a normal chair | 8.4 | $28.49 - View on Amazon #ad disclosure · October 11, 2026 |
| 3 |  MASTERY MART Extra-Long Chair Gas Cylinder, 8 in Stroke Longest Published Stroke | Reaching a counter or a tall desk | 9.2 | $37.99 - View on Amazon #ad disclosure · October 11, 2026 |
| 4 |  Rythalix Top-Activated Chair Cylinder, 6.3 in Travel Best Stated Warranty | 6.3 in with a lifetime claim | 8.0 | $29.99 - View on Amazon #ad disclosure · October 11, 2026 |
| 5 |  Rythalix Top-Activated Chair Cylinder, 3.9 in Travel Only Published Height Window | Users 5 ft 3 in to 5 ft 11 in | 7.6 | $23.99 - View on Amazon #ad disclosure · October 11, 2026 |
| 6 |  Ainilaily Long Chair Gas Cylinder, 8 in Range Only Named Test Houses | SGS and LGA, plus a real warranty term | 6.8 | $21.00 - View on Amazon #ad disclosure · October 11, 2026 |
| — |  The Office Oasis Cylinder Replacement Kit with Removal Tool Skip This Unless You Need the Tool | The removal tool, nothing else | 3.4 | $39.95 - View on Amazon #ad disclosure · October 11, 2026 |
01 · Best Overall
MASTERY MART Chair Gas Cylinder, 5.5 in Stroke
9.0/10 · scored on the published rubric
The middle size and the most useful single upgrade: 5.5 in of travel from an 11.69 in compressed length, which adds about an inch and a half of ceiling over a stock task-chair cylinder.
Why you might not: An 11.69 in compressed length is taller than some original cylinders, so on a chair that already sits low it raises your floor as well as your ceiling. Measure the old one first.
| Rated capacity | 1000 lb |
|---|
Adjustments published (4): compressed length 11.69 in, fully extended 17.2 in; stroke (travel) 5.5 in; outer column 2 in, piston shaft 1-1/8 in; Class 4, stated to BIFMA/ANSI.
Not published by the manufacturer: warranty term; cycle test count. We have flagged these rather than guessed.
How this score was built
- Fit range10/10
- Adjustability8/10
- Capacity headroom10/10
- Materials & warranty8/10
- Spec coverage9/10
The overall is the mean of these, rounded to one decimal place. Each criterion is computed from a published figure - the rubric is here.
Price as of October 11, 2026. #ad how this is funded
02 · Best Like-for-Like Swap
MASTERY MART Chair Gas Cylinder, 4 in Stroke
8.4/10 · scored on the published rubric
The short one, and the right one for a normal task chair: 9.88 in compressed to 13.6 in extended with 4 in of travel, at 1000 lb and Class 4.
Why you might not: 4 in of stroke will not turn a task chair into a drafting chair. If you are trying to reach a counter or a standing desk, you need the 8 in version, not this.
| Rated capacity | 1000 lb |
|---|
Adjustments published (4): compressed length 9.88 in, fully extended 13.6 in; stroke (travel) 4 in; outer column 2 in, piston shaft 1-1/8 in; Class 4, stated to BIFMA/ANSI.
Not published by the manufacturer: warranty term; cycle test count. We have flagged these rather than guessed.
How this score was built
- Fit range8/10
- Adjustability7/10
- Capacity headroom10/10
- Materials & warranty8/10
- Spec coverage9/10
The overall is the mean of these, rounded to one decimal place. Each criterion is computed from a published figure - the rubric is here.
Price as of October 11, 2026. #ad how this is funded
03 · Longest Published Stroke
MASTERY MART Extra-Long Chair Gas Cylinder, 8 in Stroke
9.2/10 · scored on the published rubric
The longest published stroke in this field at 8 in, extending to 21.85 in - this is the one that turns an ordinary task chair into something that reaches a counter, and the maker says so in as many words.
Why you might not: A 13.97 in compressed length is the tallest floor here, so your seat's lowest position goes UP too. On a standard-height desk that is the opposite of what you want.
| Rated capacity | 1000 lb |
|---|
Adjustments published (5): compressed length 13.97 in, fully extended 21.85 in; stroke (travel) 8 in; outer column 2 in, piston shaft 1-1/8 in; Class 4, stated to BIFMA/ANSI; supplied with gloves.
Not published by the manufacturer: warranty term; cycle test count. We have flagged these rather than guessed.
How this score was built
- Fit range9/10
- Adjustability10/10
- Capacity headroom10/10
- Materials & warranty8/10
- Spec coverage9/10
The overall is the mean of these, rounded to one decimal place. Each criterion is computed from a published figure - the rubric is here.
Price as of October 11, 2026. #ad how this is funded
04 · Best Stated Warranty
Rythalix Top-Activated Chair Cylinder, 6.3 in Travel
8.0/10 · scored on the published rubric
6.3 in of travel to an 18.5 in extended height, with the same stated lifetime warranty - the tall option for anyone who wants the range without the 8 in version's raised floor.
Why you might not: No compressed length published. Rythalix gives a height guide for this length too, but prints it as "6"-6'7"", which we are not going to interpret into a figure for you.
| Rated capacity | 1000 lb |
|---|
Adjustments published (4): extended range 12.2 to 18.5 in; travel 6.3 in; fits 1-1/8 in piston shafts, top-activated chairs; Class 4 with an explosion-proof design.
Not published by the manufacturer: compressed length; cycle test count. We have flagged these rather than guessed.
How this score was built
- Fit range7/10
- Adjustability8/10
- Capacity headroom10/10
- Materials & warranty9/10
- Spec coverage6/10
The overall is the mean of these, rounded to one decimal place. Each criterion is computed from a published figure - the rubric is here.
Price as of October 11, 2026. #ad how this is funded
05 · Only Published Height Window
Rythalix Top-Activated Chair Cylinder, 3.9 in Travel
7.6/10 · scored on the published rubric
The only cylinder here that publishes a user-height window for its stroke - Rythalix states 5 ft 3 in to 5 ft 11 in for this length - and backs it with a stated lifetime warranty against manufacturing defects.
Why you might not: The shortest travel in this field, and Rythalix publishes a noise figure (under 25 dB) but not a compressed length - so you cannot check it against the cylinder you are removing.
| Rated capacity | 1000 lb |
|---|---|
| Maker's stated user height | 5 ft 3 in to 5 ft 11 in |
Adjustments published (4): extended range 10 to 14 in; travel 3.9 in; fits 1-1/8 in piston shafts, top-activated chairs; Class 4 with an explosion-proof design.
Not published by the manufacturer: compressed length; cycle test count. We have flagged these rather than guessed.
How this score was built
- Fit range6/10
- Adjustability6/10
- Capacity headroom10/10
- Materials & warranty9/10
- Spec coverage7/10
The overall is the mean of these, rounded to one decimal place. Each criterion is computed from a published figure - the rubric is here.
Price as of October 11, 2026. #ad how this is funded
06 · Only Named Test Houses
Ainilaily Long Chair Gas Cylinder, 8 in Range
6.8/10 · scored on the published rubric
The only cylinder here that names its test houses - SGS and LGA - and the only one that publishes a warranty term you can compute with, at five years.
Why you might not: 450 lb against 1000 lb everywhere else in this field, and Ainilaily publishes neither the column nor the shaft diameter, which are the two figures that decide whether it fits your base at all.
| Rated capacity | 450 lb |
|---|---|
| Warranty | 5 years |
| Cost per warranty year | $4.20 |
Adjustments published (3): lowest height 14.3 in, highest 22.3 in, an 8 in range; stated to give a finished chair height of about 20 to 28 in; SGS (USA) and LGA (Germany) tested.
Not published by the manufacturer: stroke stated separately; column and shaft diameters; cycle test count. We have flagged these rather than guessed.
How this score was built
- Fit range8/10
- Adjustability7/10
- Capacity headroom4/10
- Materials & warranty9/10
- Spec coverage6/10
The overall is the mean of these, rounded to one decimal place. Each criterion is computed from a published figure - the rubric is here.
Price as of October 11, 2026. #ad how this is funded
Skip This Unless You Need the Tool
The Office Oasis Cylinder Replacement Kit with Removal Tool
3.4/10 · scored on the published rubric
The only kit in this field that ships the removal tool, which is the part of this job that actually goes wrong - and the maker states a lifetime warranty against leaking or sinking.
Why you might not: No length, no stroke and no capacity published anywhere on the listing. On a part bought to reach a specific height, the height is the product, and this one asks you to buy on trust.
Adjustments published (3): includes a purpose-built cylinder removal tool; 1-1/8 in piston shaft, 2 in column; Class 4.
Not published by the manufacturer: compressed length; extended length; stroke; rated capacity; cycle test count. We have flagged these rather than guessed.
How this score was built
- Fit range1/10
- Adjustability5/10
- Capacity headroom1/10
- Materials & warranty8/10
- Spec coverage2/10
The overall is the mean of these, rounded to one decimal place. Each criterion is computed from a published figure - the rubric is here.
Price as of October 11, 2026. #ad how this is funded
Questions people actually ask
Why does my office chair keep sinking?
Can I make my office chair higher?
What size gas cylinder does my office chair need?
Are office chair gas cylinders universal?
What does Class 4 mean on a chair cylinder?
Does a 1000 lb cylinder make my chair hold 1000 lb?
Is it hard to replace an office chair cylinder?
Read next
Sources
Every figure on this page traces to one of these. Product specifications come from the manufacturer's own listing; prices come from a live lookup and carry the date they were verified.