Whiteside B21 Ball Bearing 7/8"OD, 1/4"ID is designed to be used on a router bit to follow a template or the flat edge of your workpiece with precision. This ball bearing features a 7/8" outside diameter and a 1/4" inside diameter, making it a fit for various routing tasks. Inside the bearing, multiple metal balls allow it to spin ly without restraint, ensuring smooth and accurate movement. It attaches to the router bit to guide along templates or edges, providing consistent and clean cuts. Additionally, it helps adjust the horizontal cutting depth of router bits with bearing pilots, ing flexibility and precision in your woodworking projects. Model Number: B21