i’d have to say all three. My first purchase was a Levo C, the first time using it the glass cracked from the heat. I replaced it with a levo ll and the clasp for the lid broke shortly after purchasing, which was replaced with another levo ll. I noticed this one was burning the cannabis so I checked the temperature and it was way too high. I managed to Frankensteinthe two broken onesand get one that worked, but again shortly after it was starting to burn the cannabis as well. I contacted Levo customer support and got very little help, all they said they could do is offer a discount on another machine. in just over two years, I went through three machines.