Our AR4 series exhaust flaps are available in seven different sizes as standard, with inner diameters ranging from 51 to 89 mm.They have been specifically designed for use in the middle and rear silencer area and impress with their high reliability. Compatibility and Use Compatibility Adaptation U1 / Vacuum actuator (Closer): The flap is open in the unpressurized state (closes with vacuum).Adaptation U2 / Vacuum actuator (Opener): The flap is closed in the unpressurized state (opens with vacuum).The choice of the unpressurized state affects the start and failure behavior of the flap. During vehicle start, a short time is needed until the vacuum can be provided by the vehicle.Please choose the state of the exhaust flaps as they should be positioned during vehicle start. Use The actuator is simply placed on top of our exhaust flap and screwed in. Please check compatibility using the images! The actuator is not included in the scope of delivery. Advantages Material We use only stainless steel of specification 1.4828 for the base body. 1) High Temperature Resistant High corrosion resistance against all influences, even at higher temperatures 2) Ceramic Bearing Points All bearing points of the exhaust flap are ceramic Construction Our exhaust flaps are designed by us in Germany. 3) Maximum Flow Designed for maximum exhaust flow 4) Efficient Design Low installation height, top and bottom Stable disc (3mm, 1.4828) Manufacturing The manufacturing of our exhaust flaps is done on CNC turning and milling machines 100 percent in Germany. 5) Laser Welded The exhaust flap is laser welded by us 6) Made in Germany All individual parts are assembled by hand and subjected to a functional test