Optimus Big and Tall Chair supports up to 400 lb. to provide comfortable seating for a wider variety of users. Chair functions heighten the comfort level. Back-height adjustment is a simple lift motion that positions lumbar support within a limited range height adjustment to potentially support a healthy posture. Back tilt lock allows the back angle to adjust independently of seat and can be locked in a number of positions with a fixed range to support reclined postures. Chair is also equipped with a reinforced mechanism for proper support, pneumatic seat-height adjustment from 19"" to 22"" high and 360-degree swivel. Both seat and back are upholstered in easy-to-clean vinyl. Seat size is 23"" wide x 22"" deep. Back measures 22"" wide x 25"" high. Five-star base features 2"" dual-wheel carpet casters for easy mobility.