This a pair of 1/4" thick phenolic risers for the 426 Hemi Carter AFB 4 barrel which has smaller primaries and larger secondaries with a mounting pattern of 4-1/4" x 5-5/8" on center. You will notice that one of the insulators has the joined primaries just like the casting of the intake for a correct match that is found on the dual quad 426 Hemi intakes with the casting number P5153737