The Bike Bearing Installer is designed to make the installation of ceramic hybrid bearings and full ceramic bearings as easy as possible. It is very important not to use any kind of jarring impact or blunt force when installing ceramic bearings. The Boca Bearing Bike Bearing Installer & evenly presses bearings into almost any bicycle housing, eliminating the possibility of cracking or damaging the bearings. The Bike Bearing Installer can be used with bearings in the 12mm to 36mm range. Washer sizes: 21mm/36mm, 25mm/31mm, 23mm/29mm, 21mm/27mm, "15mm/18mm, 12mm/14mm. Bolt measure 7"" long" and 8mm diameter.