The Foam Air Filter and Twin Cone Air Filter, both universal fitment with a 90-63mm neck, 220mm long, with 360 degree airflow, plus a set of five reducing rubber rings covering 85mm down to 63mm so one filter fits a range of intake pipe diameters.

The foam filter uses multi-layer foam filtration in a single cone. The twin cone gives a larger filtration surface for the same length, supporting more airflow. If your engine has a high air demand or you are packaging the filter tightly, the twin cone is the better pick.

Adapting the filter neck down to a smaller intake pipe. Five rings cover 85mm to 63mm, rated -40C to +120C. They save buying a different filter for each build and let you reuse a filter if the intake pipework changes later.

Match the neck or a reducing ring to your intake pipe outside diameter, slide it fully on and clamp with a worm drive clip - or a T-bolt on a boosted install. Support the filter so it cannot rest against the bonnet, a bracket or the exhaust.

Wash the foam in warm soapy water or a dedicated filter cleaner, rinse thoroughly and dry completely - never refit a damp filter. Re-oil evenly with proper foam filter oil until uniformly coloured, without over-saturating. Engine oil is not a substitute; it drains out and can be drawn into the intake.

On a standard engine, usually very little on its own - the air filter is rarely the restriction. They earn their keep on a modified engine, alongside other intake work, or when replacing a clogged original box. The reliable benefits are serviceability, reusability and intake noise if you want it.