Work surface to be made of 5/8" Solid Plastic consisting of wood flour and resin with binder component to assure a hard, smooth, stain resistant surface, or 5/8" fiberboard 47lb core with NEMA approved high density, high pressure laminate surface with a phenolic backer sheet. Top Size: 18x24" in solid plastic or 18x24" Fiberboard top. The Upper frame is formed of 1 1/4" 16 guage tubular steel. The frame is Crossbraced and MIG welded to the U-shaped Upper legs forming a self supporting frame. Lower adjustable leg inserts are 1 1/8" tubular 16-gauge steel with dual 3/4" x 1/4" threaded steel bolt attachments for greater strength, security, and stability at each heigh adjustment. Adjustable from 22-29" in one inch increments. Entire frame is nickel chrome plated for long life and ease of cleaning. The Book Box measures 21.5" x16" x4" and is MIG welded to the frame for positive attachment. The Glides are silent, rubber cushioned, swivel of self-leveling, 1" minimum diameter, hard carbon steel with a nylon based type with a flat bottom and is chrome finished.