FAULTLESS SWIVEL THREADED STEM CASTER NEW ERGONOMIC DESIGN GIVES YOU HIGHER QUALITY, BETTER PERFORMANCE AND GREATER DURABILITY. FULL DOUBLE HARDENED RACEWAYS ALLOW BALL BEARINGS TO ROLL SMOOTHLY YET WILL NOT MAR MOST SURFACES. ZINC PLATED FINISH. POLYOLEFIN WHEELS ARE LIGHTWEIGHT YET HAVE HIGH IMPACT RESISTANCE. THESE CASTERS ROLL EASILY AND RESIST HEAT AND CHEMICALS.