30BS40BR medium duty caster wheel ,material is Rubber,3"-5",swivel and rigd or with break. 1.Screw stem description : 1/2 X13 -1" or optional screw 2.fork thickness:2.5mm 3.wheel: 4"Black rubber 4.wheel width:32mm 5.hub length:35mm 6.bearing bore:8mm 7.with side break and bearing 8.finish: white zinc