This the second revision of the fix for the M249 hop unit. The replacement wheel is designed to allow maximum travel, and the replacement nub is generous. Travel is extended to a full 2mm. The replacement nub has markings every .5mm along its length. Simply drop the new nub into the chamber concave down and aligned, cut off AT MINIMUM 2mm above where it protrudes (better to cut higher and test), install the new adjustment ring, and test.