These stitch markers come in packages of 30 rings, made from non-toxic silicone rubber. They are 13mm OD and 9mm inside, making them ideal for using on your larger knitting needles! They work great for size 7-11 needles. The variety of colors works wonderful when you need to mark off sections of your project, like outside edge, middle stitches, etc. They don't snag or hang up on your yarn like the aluminum markers do!