Casters for Height-Adjustable Table Bases, Black, 4/Set. Casters provide flexibility to bring Sit-to-Stand workstations anywhere in your office, conference or huddle spaces. Move and reposition your Alera® Height-Adjustable Table Bases with these convenient casters. Easy to attach locking casters. Caster/Glide/Wheel: Grip Ring Stem Twin Wheel Casters; Color: Black; Stem Type: Grip Ring; Wheel Tread: Hard.