Zareba Black IW5XNB-Z Nail-on 5 in. Extender Insulator, 25-Pack Fastens electrified wire to wooden posts without losing energy through the post Extends the wire 5-inch from the wooden post For 9 gauge through 22 gauge high-tensile steel wire and aluminum wire, all polywire (both regular and heavy duty), and polyrope up to 1/4-inch in diameter 25 Insulators per bag