GFB Blow Off Valve FilterGFBs 5711 foam filter is designed to protect atmosphere venting BOVs that operate in dirty environments. Made in Australia by Uni Filter for GFB, the 5711 features a foam filter element with an internal steel reinforcement, and will keep the dirt, sand, mud, and other muck out of your BOV! The large filter area is specifically sized to ensure minimum restriction to the blow off valve operation. Dont underestimate how much air a BOV dumps in a very