Review on 🔧 Park Tool SBC-1: Accurate Spoke, Bearing, and Cotter Gauge for Ultimate Precision by Michael Glassburn

I use mine to fix the rear and front hubs on a cheaper bike. The hub bearing is a replacement for the free-floating bearing, and bikes often use different sized bearings depending on the front or rear axle. The device can be used for anyone who needs to "measure" a bearing to purchase the correct size replacement. This device is available in 1/8, 5/32, 3/16, 7/32 and 1/4 bores. just lower the stock until you find the right size. SAE is on the right and metric bearing sizes MM 8, 8.5, 9, 9.5 are on the left. You get a 12" SAE ruler at the top and a 31cm or 310mm metric MM scale at the bottom. Works as advertised.