Sold as 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. Move and reposition your Alera Height-Adjustable Table Bases with these convenient casters. Easy to attach locking casters. Easy to attach locking casters. Casters provide flexibility to bring Sit-to-Stand workstations anywhere in your office, conference or huddle spaces.