Large Flange Open End Blind Rivets with Break Pull Mandrel and Flat Countersunk Head (also known as flat head break stem rivets) are tubular rivets with an integrated mandrel through the center. The rivet is inserted through a drilled hole in the parts to be fastened until the flat countersunk head lies flush with the surface.A specialised tool is used to pull the mandrel back through the body of the rivet while holding the rivet in place.
eBay