Hastings
P18020 is a rubber base cap used in Hastings insulated hot sticks, specifically models 1Hv-212, E-25, M-25, E-15-1, 8104, 8106, 8108, 8110, 8112, 8204, 8206, 8208, 8210, 8212. It's also described as a 1 1/4" replacement base cap for a hot stick.