This is a hard plastic Snap Bushing Grommet.

These grommets are very basic to install and help to protect the wire as it goes through holes in your firewall. A must have when installing any power wires through your firewall. These keep the wire from being sliced and shorting out.

.44 Inner Diameter

This grommet is too small for my #FAM branded cable, but will work with most car audio 4g cable.