We took a Father's day trip to our favorite destination, Tahoe, and these two were hanging on a tree trunk right where we parked the car, I wasn't even looking for insulators, but couldn't resist picking them up. They both are much smaller than usual, only a bit over 1 1/2" diameter when assembled. Embossed with an "M" in a triangle in the groove. Forestry spools are very common in the Sierra. I've hiked miles into the woods, to places extremely remote, and spotted a split "bob" hanging from a tree.