R188 OPEN Inner Diameter:1/4"Outer Diameter:1/2"Width:3/16" R188 is a Single Row Inch Sized Miniature Ball Bearing manufactured with both sides Open and is pre-lubricated with Light Oil allowing it to be ready for use upon delivery. Made from Chrome Steel, R188 Inch sized Ball Bearing can withstand both moderate radial and axial loads while providing high performance.