Bought to replace old leaky ones on a 5600lb travel trailer, they look the same size and are solidly built (I've checked them against mine by letter marks on the rubber seal), I started out by trying to lightly tap a rubber mallet to get it going, but that didn't work and quickly became frustrating because the diameter of the caps is about the same as the space it fits goes. So I took a needle. Nose forceps and a very slightly curved, circumferential end lip. Then I tried again, it was stillβ¦