AA commercial-grade chair intended for daily use should have at minimum: pneumatic seat height adjustment (gas cylinder, 17–22 inch range), adjustable lumbar support (up/down positioning to target the lower back curve), seat depth adjustment (seat slider that lets 2–3 fingers fit between the seat edge and back of the knee), armrest adjustment (4D — height, width, depth, and pivot), and backrest tilt with tension control and multi-position tilt lock. Additional adjustments found on premium models include forward seat tilt (reduces thigh pressure during forward work), adjustable headrest, and independently reclining backrest. Chairs without seat depth adjustment force users to either perch on the front edge or lose contact with the backrest, both of which undermine lumbar support over an 8-hour workday.