Insulators allow you to fasten electrified wire to posts wtihout losing energy through the post. Our Zareba® Round Rod Post Insulator has a self-centering post cavity with a spin-on nut that fits round rod posts from 1/4" to 9/16" in diameter. The easy spin on post nut screws on back of insulator tight to accomodate post size. For arcing protections, it has two shields to prevent shorting. It also features easy 45 degree front end loading feature that accommodates all steel fence wire sizes. UV protected to resist weathering. 25 black insulators per bag. Note: Not for use with poly tape or high tensile fencing. Zareba® Insulators are made from only the highest grade, high density polyethylene, resulting in a rugged durable construction. They provide excellent insulating characteristics and are UV-protected to resist weathering, even under the harshes conditions. The models are designed for easy attachment to any type of fence post or wire. To Select Insulator: Start with the post type. Then select the right insulator based on the type of wire and fence controller used.