Hello, Thank You for downloading the AR-15 Super (and Basic) Lower V3.1! See the README for generic info and print settings. You will need a #24 0.5 Inch wide hose clamp for this lower. Improvements in V3.1: Hammer Pin adjusted to help prevent binary fire. Bushings holes tightened to help prevent binary fire. Safety Hole extended through right side for compatibility reasons. License: These files are provided with a Martian License. You are free to treat them as if they came from another planet. They are provided without warranty. 5/15/2022 REV B - Hoffman Tactical