Thanks fellows for the help, My 2 tanks mike at 9 in.on OD,looks like 29 1/2 cirm,The balls mikes 8.563 in cold state, This gives about 1/4 in walls, My tanks dont have the markings as DD stated, one is a Carbon dioxide tank. and other is oxg. tank. 58 in. long without the valve, Hope to cut soon, Got 17 balls now,If they dont fit I will grind the side down to fit. Have you ever had loose bowling balls in your trunk living in a town full of hills,