Fi-Shock® Woodscrew Insulators. Looking for a way to safely fasten an offset electrified wire to your wooden posts so they don't become loose and lose energy? Our unique Fi-Shock® Offset Woodscrew Ring Insulator fits the bill exactly! These insulators have an 18cm offset and an angled slot that ensures wire retention while allowing easy install. They work with High Tensile wire, Powerwire and Power-rope. These electric fence insulators come in black colour only and are bulk packed with 40 in a convenient easy to carry bucket.