This air filter consists of an internal plastic frame with a foam mesh cover that captures dust and dirt. The outer, washable pad covers an accordion-style inner filter that removes even finer particles. An air filter keeps particles in the air from getting sucked into the motor, where friction will cause wear and tear to the engine. However, a filter has a limited life cycle. Eventually, it gets clogged up, which leads to limited airflow and decreased efficiency. If the engine is bogging down when it is revved up, a clogged air filter might be to blame. Simply install a new air filter and see if the motor performance improves. It is recommended to preemptively replace the air filter every spring so a clogged filter never puts a halt to a job in progress. This is an OEM part, sourced directly from MTD, and it is sold individually. In addition to MTD lawn equipment, it has also been used by other manufacturers, including Craftsman, Yard Machine, and Yard-Man.