Sit-Stand 3rd-Leg Base with control box adjusts in width and height to support a wide variety of return worksurfaces when paired with Lorell's Sit-to-Stand Two-Tier Base. Synchronized to deliver precise compensation for uneven loads, the dual motor smoothly and quietly raises the two-tier leg from 26.57" to 45" high at a speed of 1.3" per second. It works with return worksurfaces that measure 42" to 48" wide and 24" deep. Controller offers four saved height positions and a built-in, anti-collision safety feature. Metal frame holds up to 275 lb.