Fits rods and posts from 1/4” to 9/16” inch in diameter. Attaches to post with spin-on nut. Use with all fence wire and poly rope. Not for use with poly tape or high tensile fencing. Self-centering cavity. Fast, easy wire insertion. Two shields prevent arcing from wire to post. Ultraviolet stabilizers resist weathering. Made of plastic with a yellow finish. 25 in a package.