A test of endurance, where she almost freaks out, wearing a PVC bra, top, panties, and pants, while I restrict her air using a rebreather bag, then completely block it using a clip, and then just as she is about to freak out, I give her a reprieve, but then I suck all the air out of the bag after she exhales, leaving her with VERY limited re-breathing capabilities until she can't take it anymore.