This solid stainless steel spanner bushing is the most popular bushing in the industry which is typically used in most all stainless 1-1/4" Wide Caster Wheels in which use a 1/2" OD Roller Bearing or Plain bore but wish to reduce the diameter of the hole down to a 3/8" inner diameter to fit a 3/8" Diameter axle. This Spanner bushing is meant to reduce the outer diameter of a roller bearing from 1/2" OD to 3/8" ID which allows a 3/8 Axle Bolt to fit perfectly.