You're pulling wire or cable through a hole and the sharp edge of the knockout or drilled penetration is biting into the insulation — and you'll find out the failure six months later when the wire shorts out behind a wall you can't get to. Exposed hole edges are a slow-motion wire failure waiting to happen, and the callback costs more than the original install. The 3/8-inch vinyl grommet slides over the wire and into the hole, covering the sharp edge with a smooth radius that protects the cable jacket from abrasion. The vinyl material provides a gentle grip without crushing the wire, and the assortment gives you multiple grommets for the different hole sizes and cable counts you encounter in a typical rough-in. One grommet per penetration keeps the install clean and the wire protected. Sta Stocked at Crofton Lumber and Akron Lumber.