True Precision Threaded 1/2x28 9mm Luger Sig Sauer P365 XL Handgun Barrel - 4.2in - Black Nitride - This barrel has a 1/2x28 thread with included Viton high heat integral O-ring lock thread protector on threaded versions. Easy to install drop-in design. Advanced Proprietary Broach Cut Design Specifically Engineered For Increased Accuracy Potential Broach Cut 6 Groove Rifling Allows For All Ammo Types To Be Used Safely, Including Cast Lead 100% Designed And Manufactured In The USA With USA Sourced Certified 416R Stainless Steel 9mm 1: 10 Rh Twist Rifling SAAMI Spec Chamber Improved Overall Fit From OEM With Added Chamfers, Improved Radius Cuts, And Other Additions For A Better Than OEM Barrel Assorted Specialty Coatings And Finishes To Choose From Improved Feedramp Design Over OEM For More Reliable Feeding Of Defensive Ammo