In {TAIL ~ the rotary version}, {HEAD ~ the vent follower} operates in a wiper type fashion 
In
In { TAIL ~ the rotary version } , { HEAD ~ the vent follower } operates in a wiper type fashion
REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH