JOT Manufactured Wear Guide Assembly, helps to reduce wear in Master Bushings and Bowls during drilling operations, particularly when using a top drive.The Wear Guide Assembly mounts directly in the pin drive locations on 27-1/2" and 37-1/2" Master Bushings.Locking drive pins are optional. The expendable Wear Guide Rings are available for Pipe Size 3-1/2" to 5" and 5-1/2" to 6-5/8". The wear guide ring material is designed to minimize any wear to the drill string.