Missing Link Remover Plier Chain Tool Bike Bicycle Chain Master Opener Many derailleur chains use a "master link" that allows the chain to be installed and removed by hand. While this type of masterlink doesn't require a traditional chain tool, over time, dirt and corrosion can make it difficult to separate by hand. It can make removal and replacement of these masterlinks quick and effortless. Fits all chains that have a master link. Advanced tool for both open and close the chain master link.