Riker Products (www.rikerprod.com) has added a 100-mm version of its exhaust brake. The brake functions by substantially reducing the flow of exhaust gases through the tail pipe or stack. This causes compression to build up in the engine and the entire driveline begins to act as a brake or "grade retarder." By pushing a button, the driver activates a stainless steel butterfly flapper valve in the body of the brake. Exhaust flows through a separate gate by-pass port that is controlled by a second, smaller butterfly valve. It opens and closes at predetermined pressures that are matched to the vehicle's engine performance. This prevents engine damage and ensures a safer flow of exhaust gases. According to the company, this brake reduces the load on vehicle service brakes by as much as 35%.