2 Pack Genuine Briggs & Stratton 491588S Air Filter Replaces 399959 OEM

What It Is

This is a 2-pack of genuine Briggs & Stratton 491588S air filters, designed to replace OEM part 399959. It filters air entering small engines on walk-behind mowers, riding mowers, and some generators or pressure washers.

Fitment & Compatibility

Before buying, check your engine’s model number (found on a sticker near the spark plug or under the fuel cap). This filter fits most Briggs & Stratton single-cylinder engines with a 1.5–2.5-inch air filter housing, common on models like the 450E, 500E, and 725EXi series. It also works with many Craftsman, Troy-Bilt, and Snapper mowers using the same filter. Measure your old filter’s length (roughly 2.5 inches) and width (about 1.5 inches) to confirm. Avoid if your engine uses a foam pre-filter or a larger round filter (e.g., 492932).

Key Things to Know

• Genuine vs. aftermarket: This is OEM, so it fits perfectly and matches the original paper element density—no mods needed.
• Installation: Takes 2 minutes: remove the filter cover, swap the old filter, and reinstall the cover. No tools required.
• Common gotcha: Don’t overtighten the cover screws—they strip easily. Also, if your engine has a foam sleeve, this replaces the whole unit; you don’t need to buy a separate pre-filter.
• Lifespan: Replace every 25 hours or annually (sooner in dusty conditions). A dirty filter reduces power and fuel efficiency.

Should You Buy It

This is a solid buy for anyone with a compatible Briggs & Stratton engine who wants a quick, no-hassle filter swap at a fair price. The 2-pack gives you a spare for the next season, and the genuine build ensures reliable airflow without risking debris ingestion. If you just need one filter or prefer a cheaper aftermarket option, skip it—but for most owners, this is the right choice.