4N0313 Air Filter Element Fits Caterpillar 910, D3C, D4C (4N-0313, 4N313)One New Aftermarket Replacement Secondary Air Filter Element Fits Caterpillar (Fits CAT) Track Type Tractors, Track Loaders, and Wheel Loaders This secondary engine air filter element (4N 0313) fits the engine air intake system on a wide range of Fits Caterpillar (Fits CAT) construction equipment. Serving as the last line of defense against dust, dirt, and contaminants, the secondary filter protects the engine while the primary filter is being