This Genuine OEM Briggs and Stratton Gravity Feed Inlet Seat fit the Walbro LMT Carburetor found on many Model 28, Model 31, and Model 33 Briggs Intek Engines. 

The Gravity Feed Seat is used on carburetors that do not use fuel pumps but instead uses a tank mounted above the carburetor and gravity feed the carburetor. If you use a gravity feed seat in conjunction with a fuel pump it will cause the carburetor to run excessively rich and will more than likely flood the engine.