I bought this as a smaller, throw in the gig bag, version of it's larger brother, the Fuel Tank Classic.
It does everything you'd expect it to - delivering clean, reliable power to your pedals. The ability to switch voltages was much appreciated on a recent tour of Japan.
My only concern was that my T-Rex Fuel Tank Junior shipped without several of the included power cables, such as the voltage doubler and shorter length cables. These were mentioned in the product description, so once this was brought to Thomann's attention the problem was quickly solved.