So, the smoke detector began beeping so I replaced the battery but it kept beeping. I'd gotten a different brand, so I went to CVS and got a Duracell, bringing the one I removed. Well, they're slightly different sizes (VERY slightly) and the connectors look slightly different - the one that was in there said Durolock and the ones at CVS don't. I bought one and installed it and it kept beeping - but then stopped beeping and seems to be fine now. You can't buy the ones that say Durolock anywhere other than online at Amazon and some other jernts.