... Caster material: Plain bearing PU on nylon wheel and only NYLON is availableand . Double brake fitting housing,zinc plated.Head treated double ballrace with ... hardened steel balls make,the caster swivel smoothly under big load,PU coated brake pedal protect ... 15mm to 300mm, materials include rubber, TPR, PU, plastic, nylon, cast iron, pneumatic, phenolic and sandwich, etc. ...