if you give me the bolt hole sizes and how many I can tell you what series the flange it is.. The lower the series # the lower the pressure it can hold, they go all the way up to 2500, and those are about 4 1/2 to 6" thick depending on the size of pipe line. I think there are six types of flanges, weld neck, slip on, threaded, lap joint, socket, and blind.