This pair of Brass Breather Bolts will really clean up your ride! No more hoses or filter. The filter is built into the bolt. The EPA has required Harley to route hot, dirty, oily crankcase air back into the air cleaner compromising the performance of your engine. This vents it without compromising the performance or longevity of your motor. With the Outlaw Racing Breather Bolts you will experience a slight performance increase. This is because engines like Cold Dry air! Also available in Polished Aluminum. These are a must-have when doing your Stage 1 upgrade. E-Z Install Fits All Sportsters 1991 & Up (except XR1200) Fits Big Twin Evos Fitment Notes: These Breathers come in 3 sizes- 3/4" Thread length 1 3/8" Thread length 2" Thread length The most popular size after-market support brackets are about 1/8" thick. The standard 3/4" Breather Bolt is used in this instance. Other after-market air cleaners use support brackets/backplates that have more depth for the bolt to go through. (SE, Big Sucker, Joker) Depending on how deep the backplate is you will need either the 1 3/8" or the 2" Breather Bolts.