The Pinlock wood-post insulator from Power Wizard is a versatile insulator designed to work with high tensile, standard smooth wire, or polywire on a wooden post. With a large flange to prevent shorts, this black high-density polyethylene insulator features an attached pin to lock and unlock the wire for easy installation. Each pack includes enough nails for all 25 insulators. Each insulator has two hole for use with included nails or wood screws or staples to make a strong attachment to the post. The plastic is high quality - not brittle, even after many years of weathering in sunlight. These insulators have the strongest designs and quality plastic needed for the abuse and life that the normal high-tensile fence is expected to handle. It is sold in packs of 25 pieces and provides a secure and reliable solution for electric fence installation