These locking stitch markers can be hooked onto the knitted stitch within a row and can be locked so they do not slip out while you continue knitting. Use them to mark rows, decreases, increases or even mistakes. You can even use them to catch that dropped stitch before it runs down through your knitting! Each pack contains 15 purple and 15 green pieces (30 in total, all the same size), and come in a handy little vinyl storage pouch.