this is a popular size that could be used in many application.The Bearings are made of Chrome Steel, each bearing has 2 Rubber Sealed to protect the bearing from dust or any possible contamination, also bearings are pre-lubricated with grease, Bearings are packed 10 bearings in one plastic tube. * Item: R6-2RS Ball Bearings * Type: Deep Groove Ball Bearings * Material: Chrome Steel * Shields: 2 Rubber Seals * Lubrication: Self Lubricated (Grease) * Inner Diameter: 3/8" inch * Outer Diameter: 7/8" inch * Width: 9/32" inch * Size: 3/8" x 7/8" x 9/32" inch *