Glue on Nub Mod to improve the thumb landing position on the USA Made holsters by U.S. Duty Gear. USDG uses one lever shape across the board, so this is what you need regardless of firearm.
Select level 1 (called Level 2 by USDG) or 3 as needed, and your hand as you shoot. Some officers desire a lower profile release, and can use the Level 3 for a level 1 rig.
These are for Gen 1 USDG holsters with the 'stepped' levers.
Also check out the 'Open End Cap for U.S. Duty Gear' if you want to open up the end of your holster to allow brass and debris to fall out.