Self-piercing rivets (SPR) join two or more pieces of material using a rivet without a pre-drilled hole. Self-piercing rivets are a semi-tubular rivet driven at high force through the material layers to be joined, into a die which causes the tail of the rivet to flare out and form a joint. The process requires no hole preparation and delivers high static strength similar or better than, spot welding. This process produces a fatigue resistant joint that is stronger than spot welding and less susceptible to corrosion. The use of coated, lightweight, and high-strength materials, such as galvanized or pre-painted steel and aluminum makes welding these materials difficult and often not possible. For general purpose use. Refer to application specifications when choosing the proper SPR. Material: Steel, H4 Hardness with patented ALAMC Coating. When using SPR rivets the vehicle manufacturers (OEM) repair instructions are to be observed. A Test rivet should be set whenever the material or material thickness changes. Only in this way can a process-reliable Riveting process can be obtained. Used by many OE manufacturers.