Allstar Performance ALL27500 Deluxe Distributor/Magneto Hold-Down Billet Fits Most Aftermarket Distributors And Magnetos Allen Head Bolt Prevents Distributor From Turning In The Clamp So Distributor Can Be Removed And Reinstalled Without Resetting The Timing Fits All Chevy V8 Except 348-409. Will Not Fit Mallory Magnetos