These are internally threaded M8X.75RH and the external threads are the American Standard 1/2-28 threads for use with all 1/2-28 accessories. These are threaded to the proper thread length on the OD so that you don't have to install any spacers. These are guaranteed concentric. Black Oxide finished and comes with a free thread protector! Install each time your accessories are not in use to protect your threads. PLEASE NOTE: we have two M8X.75 to 1/2-28 adapters so be sure to purchase the right one to fit your needs. Email me if you have any questions, thank you.