I regularly have to transport two bases, one of which has a hard case that, owing to its shape, simply doesn't fit very easily into my car. Also, carrying two instruments separately occupies both hands during carry-in/out. I wanted something to make transporting my instruments easier, but at the same time provides good protection. I'm careful with my gear at all times, but still, accidents happen!
This twin bass bag is both efficient and effective. It provides good protection while conveniently housing two instruments. This makes my carry-in/out at gigs that bit easier and, more often than not, achievable in one trip to or from the car. It has sufficient additional pockets for my iPad/folder of charts, several cables, IEMs, and other tools of the trade. It also fits into my car easily.
Build quality is excellent, with good thick fabric, heavy duty zips, high resistance padding, and a kitten soft interior. Although it isn't completely rigid, it maintains its shape very well; so much so that it had to be transported in a rather large box as folding or squashing, even when empty, simply isn't possible. While it obviously isn't totally impermeable, it provides excellent weather protection.
My only cautionary comment (not really a negative, as a decent case for two instruments isn't ever going to be either small or light) is that if you are considering this item please be aware that the case is bulky and, when packed with two instruments, rather heavy! Great for relatively short trips, but I wouldn't want to walk across town carrying it.