He uses the mask with an exercise bike (similar to the way Charlie describes above), and the tent to sleep in at nights, for maximum results.
We had talked (I am saying “we” because I was the median english-speaker for the whole buying process… ) to an altitude training expert who was recommending what he should buy to emulate altitude training as much as possible.
Of course he would try to sell everything on his list, but the mask/bike creates exercise tolerance, while the tent enhances recovery and adaptation on a broader sense. And you get maximum altitude exposure.
This athlete’s main concerning was also raising the red blood cells (hematocrit), which obviously has improved since and he feels generally more rested.