These Fustat Fuse Adaptors screw into Edison thread fuse sockets of standard fuse boxes making it easy to retrofit existing fuse installations. Used for branch circuit protection. The Cooper Bussmann 15 Amp Rejection-Base Plug Fuse Adapter converts an Edison-style base to accept S- and SL-type fuses. This adapter is rated to 125-Volt and is UL- and CSA listed for safety.