Material Type:Metal 3/8"" OD steel caster sockets insert only into solid wood base legs. Saw tooth design grips wood well and accepts wood stem #02. Repair instruction: Removal: This is best done with a screw driver by prying the metal teeth up off the wood and then prying out from the leg. Often, the teeth portion comes loose or has been previously broken off leaving metal inside the leg hole. The metal must be removed and is done with a 11/32"" drill bit. When drilling down about 3/4"", the drill bit will ""catch"" the metal and cause it to spin around. Then, while spinning...slowly withdraw the drill and drill bit along with the broken piece. The broken piece can be removed from the drill bit with a pliers in a twisting motion. High drill speeds should be avoided if possible.