Review on Jade Active Premium Rubber Wheel Chocks: Heavy Duty Car and RV Block with Long Connecting Rope - Ideal for Cars, Boats, Trucks, Aircraft, and RVs (1 Pair) by Johnny Burns

Semi-flexible hard rubber. That's the way, don't be fooled, the more the merrier. They fit snug and snug and keep our 5th wheel locked. We use 2 sets, one for each side of the trailer to prevent twisting and running away. They are designed to be used on both sides of the same tire or between tandem tires, one front and one rear.