SIHOO M18 vs B100: Adjustable Lumbar Pad or Flip-Up Arms?

Research note: This comparison uses SIHOO's published store specifications (US and EU official stores), not a hands-on Chairpedia test. Figures are quoted as each brand states them, with the store or page they come from.

Introduction

The SIHOO M18 and the SIHOO B100 are two of SIHOO's lower-priced mesh-back chairs, and they are easy to mix up in listings. They take different approaches to the lower back and to the armrests. In one sentence: the M18 has a lumbar pad you set yourself, a pivoting headrest and height-adjustable arms, while the B100 lists lower, has flip-up arms and a fixed sacral cushion, and reclines further. Both list a 330 lb maximum load and a three-year warranty on the SIHOO US store, so the choice comes down to adjustment, space and price rather than capacity.

At a glance

SIHOO M18 — strengths and weaknesses

Documented features: SIHOO's US store lists general dimensions of 28 in wide, 27 in deep and 44-51 in high, a seat depth of 17.91 in, a 330 lb maximum load, a maximum recline of 126°, armrests that adjust up and down, a lumbar support that adjusts vertically and horizontally, a headrest that moves 3.9 in up and down and pivots 45°, a product weight of 37.1 lbs and a three-year warranty.

Check before buying: SIHOO does not publish a seat height range for the M18, so check your desk height against the overall dimensions or the live store page. The armrests move up and down only. The regular price on the US store is $289.99 for Black (including the Skate Wheels version) and $299.99 for the other colours; the store usually also shows a lower sale price.

SIHOO B100 — strengths and weaknesses

Documented features: SIHOO's US store lists general dimensions of 27.6 in wide, 28.3 in deep and 44.1-51.6 in high, a 330 lb maximum load, a product weight of 36.4 lbs and a three-year warranty. Instead of an adjustable lumbar pad, the B100 uses what SIHOO calls a floating sacral cushion, a pad set at the base of the spine. It has a wide 2D adjustable headrest and flip-up 2D armrests that let the chair slide under a desk. SIHOO's EU store gives a seat height of 18.3-21.9 in and three lockable recline angles of 110°, 125° and 135°. The B100 is sold with a mesh seat or a cushioned foam seat, and the mesh version also comes as a Footrest Version.

Check before buying: SIHOO does not publish a seat depth or seat width for the B100, so you cannot compare its seat size with the M18's 17.91 in figure. In SIHOO's description the sacral cushion is not adjustable. The regular price on the US store runs from $199.99 for the Cushioned Seat Standard Version to $259.99 for the Mesh Seat Footrest Version, in Black or White. SIHOO also sells a separate B100 Pro, which is a different model.

How they differ

Lower-back support. The M18's lumbar pad adjusts vertically and horizontally, so you place it yourself. The B100's sacral cushion is a fixed shape placed lower, at the base of the spine. If you want to set the support position by hand, that points to the M18; if you would rather have nothing to set, the B100.

Armrests. The M18's arms adjust up and down. The B100's arms are 2D and flip up out of the way, which matters when the chair has to fit under a low desk or in a small room.

Recline and headrest. The M18 reclines to a maximum of 126°; the B100 lists three locked positions up to 135°, and its Footrest Version adds a pull-out leg rest. The M18's headrest moves 3.9 in and pivots 45°; the B100's is described as a wide 2D adjustable headrest without published travel figures.

Size and weight. The overall footprints are close: 28 in wide by 27 in deep for the M18, 27.6 in by 28.3 in for the B100. The chairs weigh 37.1 lbs and 36.4 lbs. Only the B100 has a published seat height (18.3-21.9 in, EU store), and only the M18 has a published seat depth (17.91 in).

Price. $199.99-$259.99 for the B100 against $289.99-$299.99 for the M18 at regular US store prices.

Who should buy which

The M18 fits someone who wants to position the lumbar pad and the headrest themselves and does not need the arms to fold away. The B100 fits a smaller room or a shared desk where flip-up arms help, someone who wants the deeper recline or a footrest option, and buyers working to the lower list price. If you want 4D arms and a self-adjusting lumbar pad, the next step in SIHOO's range is the SIHOO Doro C300, at a higher list price.

Sources

• SIHOO US Official Store — M18 and B100 product pages (specifications, regular prices), checked 2026-09-29 and 2026-10-08.
• SIHOO EU official store — B100 product description (seat height, recline angles), checked 2026-10-08.

Bottom line

Same 330 lb US load rating and three-year warranty, similar weight and footprint. The M18 is the more adjustable of the two at the back and head; the B100 is the cheaper one, reclines further and folds its arms away. Neither SIHOO page gives a full seat-size table for both chairs, so compare the live store pages and the return terms before ordering.