Use to add aftermarket speakers to factory door location. Slight modification of the speaker adapter is required for some speakers- that's normal and that's why these fit so many different sizes. Made specifically for most 6", 6.5", and 6.75" speakers. Speeds up installation time. Made from high grade plastic for a long lasting secure fit and corrosion resistance. 2 pair each for 4 doors- 4 plates and 4 speaker harnesses. Compatible Vehicles: Made for Chevrolet: Trailblazer 2002 – 2009; GMC: Envoy 2002 – 2009; Oldsmobile: Bravada 2002 – 2004