The Briggs BA2419 Dual Flush Valve comes complete. The two buttons on the top are to flush the toilet. Therefore once the button is pushed on the top of the tank it will lift the valve. Also inside the valve is the seal that prevents leaks into the bowl. Therefore to flush that seal is lifted to let water through. Also the nut and the gasket come with this valve. 

The tube on the side of the flush valve is the overflow tube. It has the water line of the tank on it. If the water is over that line it will continue to run. Therefore the tank should not be over filled. Also this valve is a canister valve. Therefore it comes apart in the middle. However that is only to replace the seal inside the flush valve. 

In conclusion, This flush valve comes complete. It has the rubber gasket that goes in the bottom of the tank. Therefore it can prevent leaks in between the tank and the bowl. Also the nut that comes with this valve is plastic. However that means it will not rust. Also the seal inside the valve is rubber to prevent leaks. Briggs BA2419 Dual Flush Valve

• Genuine Briggs replacement part
• Comes complete
• Has the seal inside to prevent leaks
• Gasket and nut to secure to the tank
• Dual flush buttons on top