brake line seal washer

i think those copper washers are 3/8. take a banjo bolt with you to the auto parts store. they sell those in a mixed pack with various sizes. youll need to open the pack though to test fit the washer on your banjo bolt. you'll want the tightest fitting one as well, with the least movement. they also make em out of aluminum. choose your pick. ill try and get a photo for your prop valve. im using an aftermarket prop valve though.