Two complete sets of gauges in one pocket tool. The Bahco thread gauge sets comprise 28 whitworth gauges from 62 to 4 TPI and 24 metric gauges from 0.25 to 6 mm pitch. Although the US SAE standard and Whitworth standard differ by 5° of thread angle this gauge set will measure SAE threads as well as any SAE ready gauge. Just don't mind the tiny light gap.