The SLS NUB MOD® is needed for users running Level III Safariland® Holsters with the ALS® lever and the SLS hood. It also works with the ALS® only (Level I) holsters for those with a larger waist girth to allow a smoother contact with the body over the ALS Nub Mod.
Upon engaging the SLS hood downward with the thumb, the users thumb cannot help but land on the NUB MOD®, releasing the weapon into the drawstroke.