Canister Style Flush Valve. Canister flush valves are mounted in the middle of the of the toilet tank. If your toilet tank will not fill and the water keeps running this will most likely.
How can I fix it. What is a Canister Valve. This video shows the how to replace a leaky seal on your Kohler toilet.
They are especially used by modern Kohler toilets like the Kohler Cimarron.