Changing to 520 chain and sprockets

For straight bolt on sprockets, Supersprox are great. They are a steel outer sprocket and aluminum center carrier all bolted together. The Hyperstrada/Hypermotard 821 uses the same style rear sprocket as the Monster 1100. However they only go up to a 44T. Stock on the Hyperstrada/Hypermotard 821 is 45T in the rear.

Supersprox retail for $159.95

What's a 520 chain, what's gain or improvement from stock?

It is a lighter weight thinner chain. Usually cheaper to replace. Downsides are that they do not have the same high tensile strength as a 525 chain, and will need to be replaced more often, as they will wear quicker, on higher power bikes. Changing to a 520 chain requires changing to the thinner 520 sprockets.