Hendrix Tie Top Insulators are molded from a proprietary blend of gray, track and UV resistant, high density polyethylene. They are more durable and reliable than traditional wet-process porcelain insulators. They are also lighter, safer and easier to handle. The HPI-55-5-01 is designed with standard ANSI neck and thread size. It is a direct replacement for medium-voltage porcelain F-neck insulators and recommended for all conductor types, bare or covered.