Husqvarna 503958501  Air Filter

The purpose of the Air Filter is to allow a constant supply of air into the carburetor while stopping any dust, dirt, bits of grass, or other small debris from passing through and potentially causing damage to parts of the engine, like the pistons. If the air filter is clogged, it can prevent proper air flow and cause the engine to lose power. Home users often replace their air filter during their annual tune-up. Replacing an air filter will improve the performance and prolong the life of your equipment.