This is the brass insert in our pipe fittings, generally added to the PPR/PVC all-plastic pipe fittings, it becomes a pipe fitting with inserts. For example, adding a male insert to the PPR elbow becomes a male elbow. Our inserts are available in two types of brass. Generally speaking, we use 57-3 brass for IFAN fittings and CW617 brass for IFAN Plus fittings. Everyone can choose according to their needs.