SIHOO M18 vs Doro S100: One Lumbar Pad or Two?

Research note: This comparison uses SIHOO's published store specifications (US and UK 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 Doro S100 are both mesh-back SIHOO chairs, a step apart in price. The S100 is the lower-priced chair in SIHOO's S line, with the split lumbar design that the Doro S300 also uses. In one sentence: the S100 adds dual lumbar pads, 4D arms and an adjustable seat depth and reclines further, while the M18 keeps a separate pivoting headrest, weighs less and has the lower list price. Both list a 330 lb maximum load and a three-year warranty on the SIHOO US store.

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 Doro S100 — strengths and weaknesses

Documented features: SIHOO's US store specification table lists general dimensions of 27 in wide, 30 in deep and 45-50 in high, a seat depth of 15.15-17.12 in, a 330 lb maximum load, a product weight of 49.13 lbs and a three-year warranty, and the page says the chair suits users from 150 cm to 190 cm tall. The 4D coordinated armrests are linked to the backrest and move up and down 2.76 in, forward and back 1.18 in, side to side, and rotate 72°. SIHOO calls the lumbar design dual dynamic lumbar support: two independent pads that follow your posture. The upper part of the backrest works as an integrated headrest and adjusts up or down. SIHOO's UK store comparison table adds a seat height of 46-54 cm (18.11-21.26 in), a seat width of 51 cm (20.08 in) and a recline range of 98°-135°.

Check before buying: The S100 is the heavier chair at 49.13 lbs. SIHOO's UK store lists a lower maximum load than the US store and a single seat depth figure for its enlarged-seat version, so the figures above are the US ones where both exist. There is no separate headrest to angle. On 2026-10-08 both colours were shown as sold out on the SIHOO US store; the regular price is $499.99 for Black and $509.99 for White.

How they differ

Lower-back support. The M18 has one lumbar pad that you move vertically and horizontally. The S100 has two independent pads that SIHOO describes as moving with you rather than being set by hand. If you like to place the support exactly, the M18 lets you; if you would rather not adjust it, the S100's design is the one built for that.

Armrests. Up and down only on the M18, against 4D on the S100 with published travel of 2.76 in vertically and 1.18 in front to back, plus a 72° rotation.

Seat. The S100's seat depth slides over 15.15-17.12 in and SIHOO publishes its seat height (46-54 cm on the UK store). The M18 has a single published seat depth of 17.91 in, longer than the S100's maximum, and no published seat height.

Recline and headrest. The M18 reclines to a maximum of 126°, and the S100's maximum is 135°. The M18's separate headrest moves 3.9 in and pivots 45°, while the S100's integrated headrest moves up or down with the upper backrest.

Weight and price. 37.1 lbs against 49.13 lbs, and $289.99-$299.99 against $499.99-$509.99 at regular US store prices.

Who should buy which

The M18 fits someone who wants a headrest they can angle, a lumbar pad they place themselves and the lower list price, and who does not need arms that swing or a sliding seat. The Doro S100 fits someone who wants SIHOO's split lumbar design, arms that move in four directions and a seat depth they can set, and who can wait for stock if the US store is still sold out. Buyers who like the S100's design but want 6D arms can also look at the SIHOO Doro S300, at a higher list price.

Sources

• SIHOO US Official Store — M18 and Doro S100 product pages (specifications, regular prices), checked 2026-09-29 and 2026-10-08.
• SIHOO UK official store — Doro S100 comparison table (seat height, seat width, recline), checked 2026-10-08.

Bottom line

Same 330 lb US load rating and three-year warranty. The S100's additions are concrete — dual lumbar pads, 4D arms, an adjustable seat depth and a deeper recline — and so are its higher list price and extra weight. The M18 keeps the separate headrest and the lower price. Check the S100's stock and the live sale prices on the SIHOO store before deciding.