Many derailleur chains use a master link" that allows the chain to be installed and removed by hand. While this type of master link doesn't require a traditional chain tool, over time, dirt and corrosion can make it difficult to separate by hand. MLP-1.2 Master Link Pliers make removal and replacement of these master links quick and effortless. Simply insert the specially sized jaws into the master link. Then squeeze the handles top open or pull the handles to close the link. Compatible with all 5, 6, 7, 8, 9, 10, 11 and 12-speed derailleur chains that use a master link.