Cutting Diameter Description Series Page Length 12mm - 32mm XSA (Metric) 547 Carbide Reaming Head - Metric .098 - .750 .240 -1.780 Solid Carbide Thread Mills - 46Y_UN, 47Y_UN 548 Internal for UN Thread .210 - 46Y_IS_RA, .087 - .750 1.710 Solid Carbide Thread Mills - 47Y_IS_RA 549 Internal for ISO Thread 46Y_NPT,Solid Carbide Thread Mills -47Y_NPT550 External or Internal NPT Thread 46Y_NPTF, Solid Carbide Thread Mills - 47Y_NPTF 551 External or Internal NPTF Thread .160 - 46Y_UN_RM .045 - .567 1.630 Solid Carbide Thread Mills - 47Y_UN_RM 552 Small Dia. Short, UN, 2XD & 3XD .180 - 46Y_IS_RM .061 - .591 1.690 Solid Carbide Thread Mills - 47Y_IS_RM 553 Small Dia. Short, ISO, 2XD & 3XD .150 - .057 - .362 1.080 Solid Carbide Thread Mills - 46Y_UN_LM 554 Sm. Dia. Short, LH, UN, 2XD & 3XD 46Y_IS_LM, .252 - .061 - .354 .445 Solid Carbide Thread Mills - Sm. 47Y_IS_LM, 555 Dia. Short, LH, ISO, 2XD & 3XD 48Y_IS_LM .252 - 47Y_UN_RA .394 - .630 .445 Solid Carbide Thread Milling Tip - (Chip-Surfer Style) 556 Internal for UN Thread 481