A support and vacuum power device for a pneumatic prehensile member (100), such as a suction cup, comprises a casing (3) and a sleeve (8) protruding from the casing and wherein at least one recess (10) is formed. A movable element (12) is movable in translation in the casing (3) and is provided with a power supply duct (18). The movable element (12) comprises a stem (26) guided in translation in the sleeve (8). An anti-rotation insert (30) made in a single body is inserted into the sleeve through the recess and is provided with a through opening (32) slidably engaged by the stem (26). The through opening is defined by at least one contact surface (34) extended for an effective contact with an engagement portion (28) of the movable element (12), thus achieving an anti-rotation constraint for the movable element (12).