Deep Six Steel-Lock inserts are machined from tool-grade stainless steel and deliver unrivaled strength and dependability. They are 65% stronger than aluminum and withstand hard impact. Unique 40 threads-per-inch design delivers 25% more thread engagement than traditional-style inserts for increased holding power. Fits Axis, Axis Realtree and Full Metal jacket arrows. For use with Deep Six compatible heads only. Per 12. Cancer and Reproductive Harm- www.P65Warnings.ca.gov. Type: Arrow Inserts.