Du-Bro 281 2-1/4" Spinner - Yellow Simple, easy and safe to install. The spinners are available in 7 sizes. Each spinner comes complete with 5 shaft adapters (5mm, 6mm, 1/4", 7mm, 5/16"). You don't have to drill out these back plates! Features a unique nylon insert lock design for attaching the back plate and spinner - giving a solid and secure hold. Designed with safety in mind.