Yes! The difference is very slight, but can cause some minor problems when you are inserting 6mm coil into a document that has been punched 4:1 or visa versa. The 6mm pitch is the true European pitch and it usually has 1-2 more holes in an 11" binding edge versus the true 4:1 coil. You rarely run into the 6mm pitch anymore, but almost all of the time it is from a Renz machine. If you are having troubles inserting 4:1 coil in your punch pattern you probably have paper that has been punched for 6mm. Please call one of our account representatives if you need additional help to determine which pitch coil you will need for your document.