Standard Efficiency Engine Air - Secondary It pays to choose genuine Cat Filters to protect the iron that generates your income. Cat Secondary Engine Air Filters are your last line of defense against dust, dirt and other contaminants that may damage the components of your income-producing machinery. Tasked with protecting the engine while the primary filter is being changed or in the event of a breach in the main filter, this secondary unit plays a critical role in preventing damage due to contaminants. Constructed of durable materials and manufactured to meet Caterpillar’s stringent specifications, these air filters deliver the consistent quality and reliability that Cat owners count on. Because uptime and cost-effective maintenance are critical, Cat Air Filters have been specifically designed to protect and optimize the power of your Cat iron. Working together, genuine Cat Primary and Secondary Filter Elements provide a cost-effective method for maintaining your engine’s integrity and increasing your equipment’s uptime on the jobsite. Attributes: Environmentally friendly. Increased airflow with less restriction. Serves the critical role of back-up filtration.