is also preferably provided with a pair of shoulders 66 and 68 which radially project from recessed portion 54 shoulders 66 and 68 are engageable with a rib 38 which interiorly projects from shell 42 shoulders 66 and 68 are located at opposing angular positions relative to axis a so that alternate engagement of each of the shoulders with rib 38 permits axial rotation of the valve body 50 relative to the shell 42 of approximately 180 degrees the angular positions of rib 38 and shoulders 66 and 68 are selected so that the engagement of shoulder 68 against rib 38 forms a limit stop indicative of a closed position such as shown in fig3 wherein no air flows through the air valve from the air plenum the engagement of the opposite shoulder 66 against the rib 38 is indicative of a full open position as illustrated in fig2 wherein a maximum quantity of air flows through the air valve the adjective 34 full 34 was employed because as previously described rotation of the valve body will result in a continuum of positions wherein various selected quantities of air flow through the valve the flared portion 58 of valve body 50 is adaptable for manual axial rotation about axis a of the valve body relative to the shell to provide an efficient means for controlling the quantity of air exiting air outlet 64 in addition the flared portion 58 may be manually employed for rotating shell 42 relative to socket ring 20 to thereby selectively direct the airflow to a specific location or region in the interior air space of a cabin or the like it should be appreciated that there are no protrusions or other mechanical interruptions of the air channel from the air plenum to the air.