500ft. Insultube is designed for taking electrified wire under gates by putting the H-T wire through the tube. It can also be used for insulating jumper wires between non-electric fence wires. Extra long tube insulators can be cut to length for stapling to wood posts or for insulating holes in wood posts when wire is threaded through them rather than stapled. .16" ID; .36" OD Insultube is not recommended for insulating around corner posts (see wraparounds).