Blanking cap for a 3" BSP pipe. I use this to blank off my swimming pool salt cell prior to filling it with mild acid to clean it. Could be used for other light duty applications too I guess. Not designed for any form of pressure applications!! Designed in OnShape, copy and editing from: https://cad.onshape.com/documents/004ce275cc6a511fda2f2389/w/293c2420847689e6464a81ad/e/de9f933351f0fc6a9bc2b369

or search for 3"BSP end plug