The Briggs and Stratton Inner Air Filter 821136 is an essential component for maintaining the performance of your lawn mower engine. This inner air filter is a part of a two step air filtration system used on the Vangard 40HP commecial engine and is specifically designed to ensure that only clean, dust free air is allowed into your engine. The 821136 model is compatible for use in the Vanguard 40HP W/Oil Guard commercial engine, providing long-lasting and reliable protection. Trust in Briggs and Stratton's expertise and quality with this genuine OEM air filter.