These genuine OEM Harley-Davidson chrome breather bolts will fit all Harley Davidson Twin Cams with the OEM airbox.  Can also be modified to work with Mikuni carburetor kits.

The breather bolts are 3/8" (10mm) in diameter and 1.55" (40mm) in length.  Thread pitch is 16 TPI (threads per inch).  The bolt shoulder extends down .70" (18mm) with .8675" (22mm) of threads shaft below that.