The castors are supplied with fixing bolts, There is a 1 year warranty against any manufacturer\""s defects. They have a square plate with 4 holes for fitting, the mounting plate is pressed steel & the body is cast aluminium. The castors are easily adjusted using the hand-wheel incorporated into the body, when the rubber pad is screwed down the unit is fully immobilised & the rubber pad also acts as a vibration dampening mount. These castors are used for applications where the unit needs to be mobile & also needs to be fixed in position on feet.