Scaffolding Castors These nylon wheel plug type swivel castors are designed to fit standard scaffold tube. They are available in two wheel diameters and can be supplied with or without wheel and swivel locks.The main use of these castors is to convert Steeldeck or Megadek to truck units. If you are using these castors to go directly into the corner post arrangement of a rostra you will also need to order a short scaffold tube sleeve.