Medium Gripple join AND tension wire, and come available to work with all the standard gauges of agricultural wire – including 12.5 hi-tensile and 12.5 barbed wire! How it works: inside every Gripple Wire Joiner & Tensioner are high precision gear-toothed rollers. These rollers grip each wire allowing it to move in one direction only. The moment any load is applied, the rollers “bite” into the wire – locking it into place. The geared Tensioning Tool makes for quick and easy tensioning.