Speedrite Claw-type Wood Post Insulator, 25/pkg Stockwater Valves patented glass filled nylon ring

patented glass filled nylon ring top head eliminates the risk of shorting on the top wire

and this book

Insulated Pigtail Top

It reads both HDX and FDX‑B tags

Speedrite Claw-type Wood Post Insulator, 25/pkg Stockwater Valves patented glass filled nylon ringThe Speedrite Claw Wood Post Insulator, is the most reliable insulator for wood or pipe posts we have used to date. For use in many applications, from in line posts with little to no strain, up steep hills, following contour or water ways with many directional changes, or even pulling around any degree of corner. Tips: On the corners, use 2 of these insulators and spaced slightly less than 90 degrees off center from one another to ensure good wire