#STFPETSA525 Free Shipping!!! This speaker adapter fits 2006 and newer Peterbilt 389,386, and late 379. Black ABS Plastic. Includes hardware and speaker wire harness.  Hole opening is 4 3/4. Bolts to original speaker mount holes with included hardware. Trimming of the original headliner inside the speaker hole is required. Fits flattop and ultracab trucks. #stfp06525ad