Amazon.com: Universal 6 X 9/5 X 7/6 X 8 to 5.25/6.5 Inch Car Speaker Adapter Plate (Pair) : Electronics
JEAZEA 2X 6.5" Black Plastic Rear Door Speaker Adapter Spacer Rings Bracket Holder Fit for Subaru Impreza Forester Toyota Nissan|Speaker Mounts| - AliExpress
TOUR-PAK SPEAKER ADAPTERS, '98 - '13 HD TOURING - V Twin Audio
Car Audio Speaker Accessories Parts 6X9 to 6.5 Inch Cast Aluminum Adapter Ring Speaker Mounting Spacer for Toyota Camry - China Car Audio and Speaker Accessories Parts
Amazon.com: Scosche Compatible with Select Import and Domestic Vehicles 5" x 7" / 6" x 8" to 5.25" - 6.5" Adapters (1 Pair) SA68 : Everything Else
American International USB50 5.25" to 6" / .5" Extension Speaker Adapter | eBay
Metra Universal Speaker Adapter Plates 5-1/4" or 6-1/2" Speakers, Audio Installation, 826901
2 Kenwood KFC1666S + Front & Rear Speaker Adapters + Harness For Selec – absoluteusa