I ordered this recently and I thought I should give a balanced review. First, the product is cleverly designed and extends the practical life of older Bose headphones by making them Bluetooth enabled. Certainly they can be used in a wired mode, but that has become less and less convenient. The product fits well and is unobtrusive. It sounds fine. It can be charged without removing it and this is its biggest selling point over competitors. In the material, it says "Built-in long lasting battery, charging 2 hours for enjoying up to 15 hrs music playtime or talk." so I thought the battery would be fine. It actually only lasts between 3 and 4 hours. I contacted the seller and they responded: "Hello, Thanks for your message, this adapter's battery life is about 5 hours, so it is normal to be that. And if the music is louder, the battery power will be lost more fast. Thank you " So I was disappointed. If battery life is a priority for you, keep this in mind.
Battery Life is less than advertised