I agree with others who have written don't settle for cheaper substitutes! I bought a non-Canon brand backup battery for my Canon 20D years ago and it was good as a backup. But I just went on a 2 week vacation trip this year and as my Canon battery was getting low, I popped in my backup. To my surprise, it was dead, even after recently getting charged! Luckily, I was shooting outside and didn't need the flash, so the Canon battery held out once I put it back in. The backup battery doesn't seem to hold a charge now. Don't try to save some money and then risk losing some good shots--buy Canon! You'll be glad you did.