... at 50mm H4 Heavy duty type double ball bearing swivel caster wheel Heavy Duty Caster /Four Size available (4'',5'',6'',8'')[Model ... 3.Caster material: PU wheel tyre with pp core .this wheel core is adopted new latch technical.blue zinc plated, Top plate swivel ... plating and Black Electrophoresis finishing available .6.Caster wheel can be changed to Pvc,rubber ,nylon ,pp ,tpr ,cast iron,high-heat ...