Cutting Diameter Description Series Page Length 12mm - 32mm XSA (Metric) 547 Carbide Reaming Head - Metric .240 - .098 - .750 Solid Carbide Thread Mills - 46Y_UN, 47Y_UN 548 1.780 Internal for UN Thread .210 - 46Y_IS_RA, .087 - .750 Solid Carbide Thread Mills - 549 1.710 47Y_IS_RA Internal for ISO Thread 46Y_NPT, Solid Carbide Thread Mills - 550 47Y_NPT External or Internal NPT Thread 46Y_NPTF, Solid Carbide Thread Mills - 551 47Y_NPTF External or Internal NPTF Thread .160 - 46Y_UN_RM .045 - .567 Solid Carbide Thread Mills - 552 1.630 47Y_UN_RM Small Dia. Short, UN, 2XD & 3XD .180 - 46Y_IS_RM .061 - .591 Solid Carbide Thread Mills - 553 1.690 47Y_IS_RM Small Dia. Short, ISO, 2XD & 3XD .150 - .057 - .362 Solid Carbide Thread Mills - 46Y_UN_LM 554 1.080 Sm. Dia. Short, LH, UN, 2XD & 3XD 46Y_IS_LM, .252 - .061 - .354 Solid Carbide Thread Mills - Sm. 47Y_IS_LM, 555 .445 Dia. Short, LH, ISO, 2XD & 3XD 48Y_IS_LM .252 - 47Y_UN_RA .394 - .630 Solid Carbide Thread Milling Tip - 556 .445 (Chip-Surfer Style) Internal for UN Thread 481