The Flex Washers are located on the inside of the shell, on both sides below the ball rivets, and at the pastern strap below the ball rivet.
In the shell we have double washer and pastern strap has single washer.
Washers are durable and there is no need to change them very often. The hat of the screw is designed so that it will rarely comes thru the washer. Some times this can happen, since we are dealing with great forces, so if it happens, we recommend to change the washers for new ones.