Do not have one, but it is dampening the shock due to energy dissipation through rubber or air. There are different manufacturers of different units, everyone will have pluses and minuses.
Just a heads up. Almost all salesmen have the best product in the world. My answer is 'the last guy told me the same thing'. If you are from the area knowing about the dealer and his support goes along ways with any product.
Hopefully someone will chime in with experience with the product.
2015 F350 Lariat Diesel Dually, White, Hitch Kit.
2013 Dutchman Voltage 3200 Epic II 5th wheel.