We stock in Galvanized, Copper, Stainless, Aluminum, and Painted Aluminum. Pop Rivets are used for attaching collars to wyes and other fittings , to secure two pieces of metal together. Used when the Spot Welder or Clinching machine is not available, roofers use for gutters and the gutter components like elbows and outlets as well as flashing. #42 Rivets are the most common in HVAC and sheet metal. 1/8″ is the diameter of the body (also called a mandrel), it’s the thicker part of the entire piece. The stem is the thinner part that the Rivet Tool pulls and then breaks off automatically on last pull. #42 Rivets are often used with #30 Drill Bits because the #30 Drill Bit hole is slightly larger than a 1/8″ for easier penetration.