Imperial keyway bushing enables the operator to use individual keyway broaches in a variety of bore sizes. Both bushings and keyway broaches are designated by a letter which signifies the width of the keyway broach and bushing opening. For proper fit use bushings with the same letter designation as the broach being used - i.e. A Bushings with A Broaches. B-1 Bushings for B-1 Broaches, etc.