This is a pack of ten 5x11x4mm rubber sealed “Speed” clutch bearings. ProTek R/C “Speed” bearings are high quality steel/chrome bearings designed for the R/C racing enthusiast.
These 5x11x4mm rubber sealed bearings are the standard bearing for many monster truck clutches, such as the Traxxas T-Maxx and Traxxas Revo. Some racers prefer the rubber sealed bearings for better protection against dirt for their clutch. Please check the manual that came with your vehicle for the correct size if you are not certain.
These are also used as wheel bearings in the Kyosho Lazer ZX-5 1/10th scale 4WD electric buggy.
ProTek R/C is an AMain Sports & Hobbies brand.