1/2" - 28 Right Hand Thread Hex Die 1/2-28 TPI https://www.amazon.com/dp/B07CYRWCK6/ref=cm_sw_r_cp_api_glt_fabc_S998RKAVA7VYC8C4VRA8?_encoding=UTF8&psc=1
I just used this one on my ar 9mm barrel