Product Description Specifications Mounts 2 BaneBots T40 Wheels to a 4mm shaft.These hubs are provided with a tumbled finish Mounting: 1/2in Hex For Shaft: 4mm Weight*: 0.27oz Set Screw: 6-32 x 1/8in Num Set Screws: 2 Snap Ring: 1/2in External Material: Aluminum