Fits: 1997–2003 BMW 540i 2002–2005 BMW 745i 2002–2005 BMW 745Li 2000–2006 BMW X5 2004–2005 BMW 545i 2004–2005 BMW 645Ci 2006–2009 BMW 550i 2006–2009 BMW 650i 2009 BMW 528i 2009 BMW 535i 2009 BMW 528i xDrive 2009 BMW 535i xDrive aFe46-31001Throttle Body SpacersSilver Bullet throttle body spacers create turbulence in the air flow at the point just prior entry into the engine increasing horsepower, torque and improving throttle response and fuel efficiency. Silver Bullet throttle body spacers are constructed out of durable T-6061 billet aluminum and using a unique serrated/helix entry to create turbulence at the manifold while eliminating the annoying whistle found in other helix only throttle spacers.Designed to deliver more horsepower and torque, aFe Silver Bullet throttle body spacers make an excellent addition to your vehicle. They're precision-machined from T-6061 billet aluminum to exacting specifications to provide optimal performance. The combination serrated/helix design creates turbulence so that the air/fuel charge is thoroughly mixed for a complete burn. Their specially-designed serrated edge will reduce the whistling sound normally associated with throttle body spacers. The aFe Silver Bullet throttle body spacers increase the volume between the throttle and cylinder, improving volumetric efficiency.