Hex head screw for use with 3.5mm clearance drill and 2.5mm pilot drill. Add an extra 1mm length when deciding on size as self tapping screws need to clear the far cortex to maintain pull-out strength. Note: Bone screws cannot be returned due to the risk of micro-abrasions and bio-burden. Once these items leave Shoof, we cannot ensure their safety as implants. If you are unsure of the sizes needed, please consult with our friendly customer service team or your area representative before making a purchase.