Small device and so far has lasted me at approx 10 hours on one charge on my jogs. With the coming snowboard season coming up I predict it will last approx 4-5 hours only.
Sound at max level is a bit tinny but is not enough that it sounds horrible. The adapter is smaller then it looks and is rubberized so sweatproof and seems to be good in light rain and snow. So far has not had any issues with this product and highly recommended. Using this to turn my $25 skull candy drop ins to a nice pair of bluetooth speakers for my snowboard helmet. WIll upload a photo when I attach it.
Note for this regarding volume: For androids and assuming IOS make sure the BLUETOOTH volume on the device is set to max, After the actual device can go a bit louder when you raise the volume.