R1810ZZ/W7.905 Shielded Ball Bearing 5/16" x 1/2" x 5/16"(7.905mm) One Bearing R1810ZZ/W7.905 Shielded Ball Bearing, the inner diameter is 5/16", outer diameter is 1/2" and the width is 5/16" (7.905mm), this is a popular size that could be used in many applications, each bearing has 2 metal shields to protect the bearing from dust or any possible contamination, also bearing is pre-lubricated with grease.