THIS IS A NEW HAMPTON ALUMINUM ACCESSORY DOUBLE VEE PULLEY,THE ONE FOUR BOLT PATTERN & 2-3/8"RECESS FITS FORD HARMONIC BALANCERS,I DONT KNOW IF MAYBE ALL FORD BALANCERS HAVE THE SAME FOUR BOLT PATTERN,THE OTHER FOUR HOLE PATTERN IS THE SAME AS CRANK HUB OR BLOWER PULLEY,THEY ARE TAPPED FOR A 3/8 BOLT,(YOU ONLY USE FOUR OF THE SIX HOLES IN PULLEY),IT MEASURES 6"ACROSS,THERE IS A STEP ON OUTER SIDE THAT MEASURES 2"FOR BLOWER PULLEYS TO PILOT ON.PLEASE SEE MY OTHER AUCTIONS.