A support and vacuum power device for a pneumatic prehensile member, such as a suction cup, comprises a casing and a sleeve protruding from said casing and wherein at least one recess is formed. A movable element is movable in translation in the casing and is provided with a power supply duct. The movable element comprises a stem guided in translation in the sleeve. An anti-rotation insert made in a single body is inserted into the sleeve through the recess and is provided with a through opening slidably engaged by the stem. The through opening is defined by at least one contact surface extended for an effective contact with an engagement portion of the movable element, thus achieving an anti-rotation constraint for the movable element.