Frankly, I was hesitant to order this because there weren't many reviews and replacement batteries from another vendor can sometimes be a little sketchy in my limited experience. The price made it worth trying for me, and I'm very pleased. The battery fits in my Roomba Sage perfectly, and it charged with no problem. It's been running for a while now doing the first cleaning (hooray for getting housework done while I'm on the computer). I'm happy!Get more detail about Tenergy 4905 Replacement Batteries for iRobot Roomba 400 Series Vacuums, Grey.