The interchangeable cables come in six lengths and can be used with either the Symfonie Wood or Nova metal needle tips. Each cable comes with a key to lock it onto the tip and stoppers so that you can leave your knitting on the cable while you use the needles for something else.
The cable, combined with the needle tip creates the length stated. As a general rule, if you are knitting something with a small circumference in the round then you will likely need a 40cm cable - the length of the cable goes up according to the circumference of the item being knitted.
If you are starting out with interchangeables, it is worth thinking about buying a set which will get you going with all the basic sizes.
