FR4ZZ Flanged Ball Bearing 1/4" x 5/8" x 0.196" inch FR4ZZ Flanged Ball Bearing, the inner diameter is 1/4", outer diameter is 5/8" and the width is 0.196", 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.