"Farr" style carbody air filter as found on Canadian RS10, RS18, and RSC14 diesels. This sprue includes 25 air filters. Given their small size these filters are made thicker than they should be and will need to be filed thinner before installing on a model.
This sprue includes 20 single and 5 triple filters. A single filter is 2.8mm square and a triple is 2.8mm high by 8.5mm long.
Other filter arrangements are possible, such as those found on the M636, and I would be more than happy to assemble a sprue to match your arrangement on demand.