This is a pack of ten 5x11x4mm metal shielded "Speed" clutch bearings. ProTek R/C "Speed" bearings are high quality steel/chrome bearings designed for the R/C racing enthusiast.
These 5x11x4mm metal shielded bearings are the standard bearing for many monster truck clutches, such as the Traxxas T-Maxx and Traxxas Revo. Please check the manual that came with your vehicle for the correct size if you are not certain.