This holder is similar to what was used in vintage blackface / silverface era Fender amps as well as others. Made for 1 1/4" AGC style fuses, this tough self-extinguishing thermoplastic holder mounts in a 1/2" hole with the included rubber gasket and metal nut. The electrical connections are tin plated copper for strength and superior soldering. The twist lock cap makes removing and installing fuses a snap. This cap will fit most vintage holders.