Good for casting on
When i first saw these I thought it was a bit of a gimmick to have a ruler marked on the needles. Every experienced knitter knows that you can't measure the width of your knitting on the needle, and these won't help you measure the length at all, which is where you do most of your measuring anyway. However, I have sinced realised how useful these are for casting on, especially if your cast on edge is frequently tighter than the rest of the piece you are knitting. First take the width measurement in cm you expect the piece to be and divide this by the number of stitches you will be casting on. This will be the number of stitches per cm. These needles have 2 cm markings on them, so double that number, and as you cast on, make sure that is the number of stitches covering that part of the needle and no more. Then your cast on edge will be the same width as the whole piece.