It was a perfect fit. This was a replacement for an OEM battery in a Ring security sign that recharges via solar power and lights during darkness. The OEM eventually would not stay on past 2am. This one is doing the job from the first night after being out in an overcast sky to charge for about half a day. But after just a few days, I cannot comment on longevity compared to the OEM. Can recommend based on a few days of use in this particular application.NOTE: This is NOT an AA battery. Those who criticize it as being "too short" must have assumed their device used an AA rechargeable. Seller's ad says "not AA". This specific 400mAh battery is a different item that is similar in diameter, but about 5mm shorter than an AA and 3.2 volts vs.1.5. They come in varying mAh capacities so only use it if it is equivalent to the model # you are replacing as a LiFePO4 does come in different sizes based on mAh. Saw one 1500 mAh that was 4mm larger in dia. and 15mm longer than an AA.