ATC Fuse Holders for automotive and 12 volt electrical systems Allow you to add circuit protection by splicing the fuse holder into a new or existing wire or circuit. These fuse holders accept standard ATO (Open to Air) and ATC (Closed to Air) fuses which are available in amperages ranging from 3 amps to 40 amps current capacity. Some of these ATC fuse holders come with weatherproof caps for use in exposed or harsh environments. Pre-wired fused holders are available in wire sizes ranging from 10 awg to 18 awg. Our Add-A-Fuse ATC holder can take an existing fuse from your fuse block, and split it into two separate fused circuits - great for when your fuse block is full but you need to add a circuit to it.