The CRM250 air filter element, an oval dual layer foam, the green oiled coarse outer layer and the white fine inner layer, twin intake slots in the middle for the two carburetor intakes, and a center black rubber ring for the intake passage. Coarse and fine layers filter the dust, the air taking only the two paths of the slots and the ring, with no seam leak. Wash with cleaner, dry, thin with oil, and it reuses; swap it when it hardens, crumbles or tears. Covers why two slots, what each layer does, what the ring and the oval do, and how to wash and fit it.