Universal Grommet, Fits 1/2" Hole w/Single Wire Opening. Sometimes you are forced to punch a hole in your firewall to get additional wires into the engine compartment, but that hole you cut is sharp and can potentially sever wires. To help prevent this, install this universal wire grommet. In addition to the added protection, this grommet also gives the hole in the firewall a cleaner appearance. Fits into 1/2" opening and fits one wire (up to 16 gauge). Opening can be drilled out slightly if necessary.