Ok so usually I would buy the authentic canon equipment, but I am looking to buy an external battery pack for my 580 ex ii and am I thinking that the manufacturer does not really matter on this does it? After all they both take 8 aa batteries and I plan on using the same rechargeable batteries that I use in my flash now. All they essentially are is a holder for the batteries and a connector to the flash right? Just looks like a nice way to save about 150 bucks. I am more specifically talking about the cp-e4 vs some other no name brand off ebay.