Hands down; 16 oz. is the absolute BEST cloth for a 4 yard box pleated kilt. There is no question about it. 13 oz. is suitable as well. But, when you hack off half the yardage, the 16 oz. just feels right. The only 13 oz. kilt I have is an 8 yarder and I can tell if it were a 4 yard box pleat, it wouldn't have the presence my 16 oz. box pleat has.