These colored opening markers accommodate up to a US 11 needle. Included are 10 each of 6 more muted colors to help you keep track of your knitting. When not in use, they attach to your Maker's Keep. Made of steel. Please note that in order to keep these markers very delicate, so they won't leave a ladder in your knitting, they are painted, not nylon coated. With extended use the paint may begin to wear off giving them a rustic look - but enough paint should remain on the pin end to distinguish each color from the next.