BOSS Chair EXECUTIVE HI-BACK LEATHER PLUS CHAIR Beautifully upholstered in black LeatherPlus.LeatherPlus is leather that is polyurethane infused for added softness and durability. Passive ergonomic seating with built-in lumbar support. Padded armrests covered with Caressoft upholstery. Large 27" nylon base for greater stability. Hooded double wheel casters. Upright locking position. Pneumatic gas lift seat height adjustment. Adjustable tilt tension control. Optional knee-tilt mechanism available (B7502).