Janki Oil Tools wear guide assembly are robust and reliable tools specifically designed to prevent wear on master bushing and bowls while drilling operations.The wear guide assembly fits directly in the pin drive locations on 27-1/2" & 37-1/2" master bushings. Locking pin drives are optional. The expandable wear guide rings are available for pipe size 3-1/2" to 5" and 5-1/2" to 65/8". The wear guide ring material is designed to prevent any wear to the drill string.