Patented PEM® Type PFC4™ self-clinching stainless steel panel fasteners install "flush" (on one side) into thin stainless-steel sheets. The type (400 Series stainless steel) can be installed permanently in stainless sheets up to HRB 88 hardness on the Rockwell "B" scale and meets UL 1950 "service area access" requirements to enable subsequent access to an assembly. The side of the sheet opposite installation remains flush.