Silhoflex seating features a durable polypropylene shell with anti-static surface and a lumbar support system which forces proper posture reducing fatigue. This seat was designed with waterfall and is contoured for optimum posture, comfort and flexibility. For maximum support, the shell rests directly on frame, which is made with 1" and or 1 1/8" diameter and between 18 and 16 gauge steel tubing, with 16 gauge mounting brackets. Available with book basket. Back of shell is attractive, ribless and easy to clean, attached with four concealed steel rivets. Stacks up to 20 high to save space.