P60458 Steel Rivet - Steel Mandrel. 3/16 diameter x 3/8 head x 3/8 to 1/2 range. Blind open end pop rivets are available in a variety of sizes, types, and materials to fit most any application. Simple three step riveting make quick work of most any fastening job. These open end rivets resemble conventional tubular rivets when set, but retain the mandrel within the rivet body for added strength.