The Briggs & Stratton 399443 Engine Upper Carburetor Body supports proper fuel and air passage within the carburetor for reliable engine operation. This replacement upper carburetor body forms part of the carburetor assembly and provides the housing for internal fuel and airflow passages. Proper positioning of these passages helps maintain consistent fuel delivery and engine performan... https://www.wholetoolbox.com/briggs-stratton-399443-engine-upper-carburetor-body/399443.html