mazda part numbers explained. quickly.
first four = original application, ie fa01 is 81-85 rx7, n3a1 is fd engine etc etc
next two = sytem of car; ie 15 is cooling, 13 is intake, 17 is manual transmission
next three = what is is; 15-205 is a radiator cap, 61-211 is a heater hose, 51-070 is headlighty
letter = if the part has ever been revised, n304-10-100 and n304-10-100c, 100c is the new part number c theoretically = better but sometimes its a vendor or price change too
next 2, vendor or color code. 9u means they went to kragen, fb01-64-350a-48 is blue fb01-64-350a-00 is black