Can't really get too excited at this product it is a power supply for the Blackstar FLY3, you plug it in and then you don't use the batteries in the amp...... that's about it.
Well built, quite robust, doesn't fall apart like some power supplies, will save you a few euro on batteries.
Realistically it is a bit overpriced for what it is (so one star gone straight away), but such is life if the product has a proprietary voltage i.e. not 6, 9 or 12V (the Blackstar FLY3 product itself I cannot say a bad word about). There are lots of other electrical products on the market which include the power adapters, so this should really be no different.
As I say .... it is a power supply..... albeit a pricey one.