This is for +0.030" Diameter Thread Size - Typically for use in engines with damaged breather bores
New-style breather is not dependent on the rotation of the crankshaft to make it open and close...
CRANKCASE BREATHER VALVESSolves the problem of oil carryover in Twin Cam "A" motors with stock oil pumpOil carryover is oil that comes out of your breather and all over your bikeEasy to install...