The GFB 5711 Foam Filter is designed to protect atmosphere-venting blow-off valves operating in harsh or dirty environments. Manufactured in Australia by Uni Filter specifically for GFB, it uses a foam filter element with internal steel reinforcement to keep dirt, sand, mud, and debris out of the valve.

The filter features a large surface area that is carefully sized to minimise restriction to blow-off valve operation. A BOV releases a significant volume of air in a very short time, and small breather filters—such as the common 25mm units used by other brands—can severely restrict airflow and compromise valve performance.

Supplied with a stainless steel clamp, the 5711 foam filter installs directly onto any 38mm (1.5") BOV outlet, including the GFB 5703 trumpet and 5238 recirculation outlet.