Specifications:Bearing Type: Top MountedInner Diameter: 3/16”Outer Diameter: 3/8”Thickness: 1/8"Screw Size: #5-40 x 1/4"Package Contents:12 Pcs x R166ZZ Bearings12 Pcs x Socket Head Screws1 Pcs x WrenchDescription:Bearing guide is used on router bits to route a smooth line or limit the cutting depth. Chamfer bits, flush trim bits all use bearing guides to route to a precise pattern.After frequent use, the bearings of the router bit may become loose or difficult to rotate. If the bearing cannot rotate freely, it will affect the working effect. These bearings can be used to replace worn out bearings.Notice: Choose the correct inside diameter (I.D.) and outside diameter (O.D.) for your needs.How to change bearing on router bit?Step 1 - Select a appropriate hex key to loosen the original screw.Step 2 - Remove the old guide bearing and place a new one.Step 3 - Insert the screw and tighten.Step 4 - Ensure the bearing spins freely before they get to work.