All of them are required in the infinity group. But 6 obstacles you can fail, and do a punishment exercise at the finish/starting line. I think they were (i don'tremember cute names): the first monkey bar/rope obstacle 53s in, the vicks vapor rub cloud 2m38s, electric eel 3m10s & electro shock at the end, monkey bars 3m17s, and either the ice bath or the other hanging obstacle with rock holds. I don't remember now which had a penalty attached. Basically if you failed all 6 you would be eliminated. But could fail 5 and keep going each lap.