I used 6 1/2 from Crutchfield. They have the appropriate adapters that make it a bolt-on affair. I helps to have a cordless drill, though. ______________________ Louis LaPrad Art Direction & Design ______________________ design@louislaprad.com www.louislaprad.com ______________________ Ph 615-473-2488 Fx 615-463-7950 ______________________ Portfolio available upon request.