Add-A-Circuit Fuse Holder provides a Slot to keep Original Circuit fused and a Fuse Slot for protecting new added circuit. Useful when adding electronic devices that require direct wiring into fuse box. Add-A-Circuit Fuse Holder must be of the same fuse type as original circuit. Splice new circuit wire into attached Butt Connector. Remove Fuse from existing Fuse Block, insert new Holder into the slot, insert original Fuse into Holder and insert new 10 Amp Fuse into added Circuit Slot. Both original circuit and new added circuit are now protect by the individual fuses. Fuse Holders are a high quality heat resistant PVC with brass tin-plated electrical contacts. Fuses sold separately.