I would forget about CPR overflows. They can and will fail and at the worst possible times. If you haven't bought a tank yet, get a reef ready. If you have and haven't filled it yet get someone to drill it for you. But if you are going to go with an overflow box at least go with a U tube style. There are a couple different makers of U tube overflows, my choice would be a Lifereef. They are a bit more expensive, but the quality and the reliability make them worth it. You have to figure out how much trouble is having half the water in your tank being dumped on your floor going to cause? The CPR units rely on a pump to keep them working and for them to restart after a power outage. The pumps will fail and the port in the overflows that they attach to are prone to clogging which will also cause them to fail to restart. The Lifereef units use no pumps and start every time all the time. The only time you need to do anything is when you first install it or when you clean the U tubes (something almost impossible to do on a CPR). The Lifereef i had i sold to speeddemonlsr and you see his opinion. The only reason i sold it was i upgraded to a reef ready tank. Otherwise i would still have it. The CPR unit i had i took the bulkheads out of and trashed the rest because i couldn't sell or give it away and sleep at night. My .02