For those of you that may be a little tight on money and may not be able to afford a Pyrex tank, These are the best tanks for the money. They are made out a high quality plastic, I have had no issues with fogging/cracking, with aluminum caps on the ends. These tanks use XL cartos and I absolutely love them. They are around 7-8 bucks. They have a good tight o-ring on them too so thats a plus. I really don't have anything bad to say about them except maybe the size of them. Great tanks for the money and I recommend them to those of you without a huge disposable income.