This split stop collar is designed to fit the shank of the UJK pocket hole drill bit, as well as other drill bits with 9.5mm (3/8") shanks. Its one-piece single split design provides greater clamping force compared to a set-screw shaft collar. Unlike a locking grub screw type, a split collar grips the shaft without leaving score marks. Internal diameter: 9.5mm, external diameter: 19mm, thickness: 9.5mm.-bg