Rev9Power Rev9_AC-030; Turbo Adaptor For 2.5" 4 Bolt To 3" V Band(Cast) Product Details 2.5" 4 bolt to 3" V-band conversion flange turbo adaptor (CAST) "-Extremely strong casting -2.5" inner center on 4 bolt side -3" V-band side ( must be use with 3" C-band clamp and adaptor) Can be also used as a 3" V-band to 4 bolt adaptor