5/8 24 looked a bit oversized and didn't clean the threads on the expensive N-connector that was at the end of the redesigned Heliax cut. Pulling out the "calibrated C-clamp" (vernier caliper) was not a die. The main jet diameter was within 0.001" and the old plug was almost 0.01" smaller. Super great price for a threading tap, but I have my doubts about tapping a new thread on anything harder than brass or zinc. Be sure to use thread cutting oil and good luck dry cutting/rethreading. The tap points just inside the maximum large diameter and cuts new threads onto the new UHF/N barrels. Overall a worthwhile purchase.