Pressed Steel Spring Loaded Castors made out of thick sheet with tapper roller bearing & thrust bearing fitted with grease nipple for lubrications to provide strength & protect from damaging shocks / vibrations caused due to heavier loads & evenly distributed over the wheels & spring assembly , heavy spring to take care for extra load.
Center bolt is forged from EN-8 steel to enhance shock bearing capacity. Kept two ball bearings to ensure noise - less movements.