Please follow the steps below in order to mount the swivel castor:
Check if the current castor is attached to the chair leg with a threaded stem or a grip ring stem: If you see a hexagon nut at the base of the stem that is inserted in the chair, it is a threaded stem. If the same spot shows a slight bulge instead of the hexagon nut, it is a grip ring stem.
Remove the current castor and stem: If it is a grip ring stem, pull the castor out of the chair leg. Often both the castor and the grip ring stem will come loose when you pull them out. If only the castor comes loose and the stem is stuck, clamp it with a pipe wrench and use a hammer to gently tap on the wrench in order to release the stem. If it is a threaded stem, twist the stem and castor clockwise until they loosen and can be removed. Use pliers or an open-end wrench for additional leverage, if needed.
Now insert the new swivel castor with stem. Grip ring stems are simply pushed into the hole until they lock into place. Threaded stems need to be twisted into the threaded hole of the chair leg until the castor is firmly in place.
Please note: Swivel castors must be mounted perpendicular to the floor. Incorrectly mounted castors get stuck, dragging across the floor and damaging it.