With Weber carbs equipped with velocity stacks (or air horns) there is sometimes very limited space with the wall of the engine compartment. For example, on #3 & #4, the normal straight bodied Uni Filter will lay against the side of the engine compartment. Therefore we recommend the "short angle" version that tilts up and away for clearance.

Filters are sold in packages of two.  Enough to do one Weber carburetor.