The Caster Kit can be used to convert fixed feet Labconco base stands to mobile base stands. Kit includes four 5" diameter, non-marking polyurethane casters with toe locks. Load rating for each caster is 250 pounds. Casters have bearings for quiet operation, and replace the fixed feet included with Telescoping Base Stands. They add 11" (28 cm) to the overall depth of the base stand. Installation required. Not for use with stands that support Purifier Logic Class II, Type B2 Safety Cabinets.