i used a die grinder. Measured at bothe ends.. the ovals are really difficult. You will need to bevel the end so the cap will go back inside. It took 4 hands to get mine to fit. The round cans are easier. What happens is when you cut it. The oval can will lose its shape and become round again. You will have to put a vise or clamp back on it to make it oval again then, you will have to pry the edges of the can out to get the end cap back in.