Sihoo M18 Ergonomic Office Chair with Headrest, Black

What the M18 is, and what the listing's model fields say

Amazon's model name field reads M18 and the manufacturer part number reads M18-M148, but the model number field on the same listing reads B100-Lite-M101-JT-JP, which references a different Sihoo chair entirely. The listing-supplied installation guide settles the identity: its cover names Model M18 and gives an overall size of 68.5 by 72 by 109 to 130 centimetres.

Sihoo's own page describes the M18 as a chair with a W-shaped sponge seat cushion, a breathable mesh backrest, dual-adjustable lumbar support and armrests that move up and down. The chair is a mesh-back, padded-seat design rather than a full mesh chair, which is how Sihoo itself distinguishes it from its M57.

The measurements, and where the listing contradicts itself

The brand comparison chart on the listing gives the M18 a seat width of 51 centimetres or 20 inches, a seat depth of 45 centimetres or 18 inches, a seat height range of 44 to 54 centimetres or 17 to 21 inches, and an overall height of 109 to 127 centimetres or 43 to 50 inches.

Sihoo's own specification panel gives general dimensions of 28 inches wide by 27 deep by 44 to 51 inches high, a seat depth of 17.91 inches, a maximum hip width of 20.08 inches and a chair-back lifting height of 44.09 to 51.18 inches. Amazon's separate measurements table instead lists a single seat height of 20 inches and a seat depth of 18 inches.

Those three sets of numbers do not agree on the top of the height range or the seat depth. Use the ranges rather than the single figures when you are checking against a desk, and measure your desk's underside clearance before ordering.

Armrests move in one direction only

Sihoo's specification panel describes the armrests as adjustable up and down, and the listing's own comparison chart classes the M18's armrest type as 2D and its headrest as 2D. The installation guide's function list matches, naming armrest height adjustment with no width, depth or pivot movement.

If you need the arms to swing in towards your body or slide forward, this is not that chair. The other adjustments the installation guide names are headrest height, lumbar support depth and height, backrest tilt tension, seat height and backrest tilt angle, which is six controls in total.

Recline: the listing and the maker give different limits

The listing's comparison chart gives the M18 a recline of 108, 118 and 128 degrees, which reads as three locking positions. Sihoo's own page instead says the M18 reclines up to 126 degrees and adds that the headrest moves 3.9 inches up and down and pivots 45 degrees.

Neither source explains the two-degree gap or whether 126 is a locked position or a free limit. If reclining far back matters to you, ask Sihoo which figure applies to the current production run rather than choosing between the two yourself.

Assembly and the safety lines in the printed manual

The installation guide lays out eight steps: press the casters into the base, insert the gas lift, drop the mechanism onto the gas lift, fix the mechanism to the seat cushion with four shims and four M6 by 20 screws, bolt the back plate to the seat with three shims and three M8 by 45 screws, fit the armrests with six shims and six M6 by 25 screws, and slot in the headrest. A hex wrench is included and Sihoo packs one spare of each screw.

The same page carries eight safety instructions. They say one person per chair, use it on a flat floor, do not let a child under five sit on it alone, do not sit on the armrest, do not stand on the chair or use it as a step, do not overload it or use it as a trolley, keep sharp objects and fire away from it, and keep your fingers out of the mechanism while seated.

Sihoo's page gives a maximum load of 330 pounds and a product weight of 37.1 pounds, and lists the materials as polyester mesh, steel, aluminium and nylon framing parts, polypropylene back and headrest framing and cushion padding. The Amazon listing claims the chair passed a BIFMA test and a 1136 kilogram static pressure test; Sihoo's product page as we read it does not repeat either claim.

One year or three? The two documents disagree

The printed installation guide's welcome note says Sihoo will offer product warranty service if any non-human issue occurs within one year. The Amazon listing's final bullet promises free replacement parts during a three-year warranty period, and the listing's comparison chart lists three years of service for every Sihoo chair shown.

Sihoo's own product page also says three years, alongside a 30-day trial. So the one-year line survives only in the sheet that ships in the box, and we found no document reconciling the two. Keep the packing slip and raise any claim in writing early rather than assuming the longer term applies.

The guide's contact route is by email to a regional address printed on the page, and Sihoo's page gives a separate United States support address. Neither document we read sets out a component-by-component warranty table, so ask what the gas lift and the mechanism are covered for specifically.