R166ZZ Shielded Ball Bearing 3/16" x 3/8" x 1/8" R166ZZ Shielded Ball Bearing, this is a popular size that could be used in many applications, the inner diameter is 3/16" inch, outer diameter is 3/8" inch and the width is 1/8" inch, each bearing has 2 metal shields to protect the bearing from dust or any possible contamination, also bearing is pre-lubricated with grease.