An exhaust valve rocker arm for an exhaust valve rocker arm assembly operable in a combustion engine drive mode and an engine braking mode, and configured to selectively open first and second exhaust valves, includes a body defining an aperture to receive a rocker shaft such that the body is rotatable about the rocker shaft, a bore defined in the body, and a rotating stepped engine brake capsule disposed in the bore and having a castellation mechanism. The rotating stepped engine brake capsule is movable between a locked, engine brake active position and an unlocked, engine brake inactive position.