The FireDial will result in EVEN cook temps for the entire cook. Will hold rock steady with no adjustments once your coals are up to temp. Results in less fuel consumption & quicker starts. The Heat Diffuser Plate may be placed on the existing brackets just below the bottom grate level, where the water pan sits. This is a DIRECT fit for your WSM. Helps attain solid cooks with a low & slow cooking method. The water pan is no longer needed, but can be easily put back if desired. This baffle plate allows the meat to cook in its own juices. Wash with soap and water before first use. This dial size is compatible with 18 in. WSM. The FireDial will equalize temps across your WSM.