15x21x4mm Rubber Sealed Ball Bearings (10) 15x21 6702-2RS High Speed Precision Steel Includes Ten (10) High Speed Precision Steel 15x21 Ball Bearings. These bearings are perfect for any applications where 15x21x4mm 6702 ball bearings are required. Advantage Ball Bearings are perfect for a variety of applications including: RC Cars, RC Helicopters, Bicycles, Fishing Reels, Robots, Spinners, Inline Skates, Skateboards, Scooters, Tools, Machines, Vacuums, Electric Motors, Nitro Engines, Drones, Yo Yos, and more! Rubber Sealed Ball Bearings have maximum protection, and are ideal for dusty or dirty environments. They protect well against exposure to dust, dirt, and moisture, which can destroy bearings. Advantage Racing Product Bearings have been run by some of the fastest RC Car Racers in the world and have won multiple ROAR US National Championships. Over 250,000 bearings have been sold to satisfied racers all over the world!