Tube insulators are the lowest cost option for high-tensile fences. It is installed by sliding the appropriate number (corresponding to the number of posts) onto the end of the wire. Push the group of insulators down the wire and each tube as you proceed down the line. Be sure to staple in far enough so the tube cannot easily slide away from the post, but not so hard that it restricts wire movement.
4" tube, 2 fin (flange), 200 per pack