The foam filter uses multi-layer foam filtration in a single cone; the twin cone has a larger filtration surface area for a given length, which supports more airflow. Both are universal fitment with a 90-63mm neck, 220mm long, with 360 degree airflow. If your engine has a high air demand or you are packaging the filter in a confined space, the twin cone is the better pick.

It has a solid 76mm aluminium neck rather than a rubber one. That gives you a rigid, precisely sized surface for a silicone coupler and clamp, which is more secure on a boosted or heavily vibrating installation and will not distort when the clamp is tightened. Choose it if you are clamping to a fixed pipe rather than a flexible hose.

Match the filter neck to your pipe outside diameter. The standard foam and twin cone filters have a 90-63mm neck, which suits a range of pipe sizes with the reducing rings; the hard outlet version is a fixed 76mm. Slide the neck over the pipe and clamp it with a worm drive clip or, on a boosted installation, a T-bolt clamp.

They adapt the filter neck down to a smaller intake pipe. The set gives you five rings covering 85mm down to 63mm, rated -40C to +120C, so one filter can fit a range of pipe diameters. It saves buying a different filter for each build, and means you can reuse a filter if you change the intake pipework later.

If the filter sits in the engine bay drawing hot air, yes - it will make a measurable difference. Our aluminium heat shield fits 2.25 to 3.5 inch filters, is lightweight, and is shaped to allow maximum airflow while blocking radiant heat from the engine and exhaust. It comes in silver or black. An open filter in hot air undoes much of what the filter gained you.

Remove it, wash the foam in warm soapy water or a dedicated filter cleaner, rinse thoroughly and let it dry completely - never fit a damp filter. Then re-oil evenly with proper foam filter oil until the foam is uniformly coloured, without over-saturating. How often depends on conditions: dusty or off-road use needs far more frequent attention than road use.