This OEM nut is a 5mm, gold, metal nut, which is sold individually. It can be installed with a Wrench or Socket and Torque Wrench by torquing to the manufacturer specifications. This nut is used to secure another part in place, and should be replaced if damaged due to fatigue (such as damaged threads or rounded ends). This nut can have various uses on various equipment, and as such the difficulty of the installation can vary, but generally this is an easy repair.