Abstract: A rotary fluid pressure actuator device includes a housing comprised of a pair of housing members interconnected together for relative movement therebetween. A vane rotor assembly is positioned in the housing and is rotationally reciprocated in response to the direction of flow of fluid to and from the interior of the housing members. The housing members are provided with internal stops which are adjustable with respect to each other to permit the rotational stroke of the vane rotor assembly to be variously adjusted. Rotary movement of the vane rotor assembly is transmitted directly or through a shaft to another device for actuation thereof.