We have been using these hex-style bullet comparators for over 20 years, and believe we make the most accurate tools available. The holes in the Sinclair Bullet Comparators are cut with throating reamers to accurately duplicate the actual throat of a rifle.

Each Nut has 6 different calibers:

Nut 1: Caliber: 22 Caliber (.223-.224), 243/6 mm (.243), 25 Caliber (.257), 264/6.5 mm (.264), 284/7 mm (.284), 30 Caliber (.308)

Nut 2: Calibre: 17 Calibre (.172), 20 Calibre (.204), 22 Calibre (.223-.224), .270, 30 Calibre (0.308), .338