They would be the exhaust gasket retaining rings

Changing exhausts over is an easy exercise. Lay things out in the order you remove them,then when reinstalling bolts etc work from the opposite end.

The circlips you will reuse are located around the flared end of the pipe that sits inside the exhaust port. Carefully remove them because if you get rough and distort them they wont locate and seal correctly. After you remove them the old exhaust flanges will also be able to be removed.

The "circlips" sit inside a recess in one side of  the exhaust flange.

I always change the exhaust gaskets everytime I change the exhaust or take it off, for the price of a few dollars each and the hassle if you have a leak because of the old gasket not sealing its well worth it. Always have a spare set of SE gaskets in the toolbox.