I've come to accept that, unless stated in the specs, all of these type of devices are limited to battery output. I can see no valid reason not to list the available voltage unless it has no boost.
I keep hoping that the penny-pinching manufacturers will realise that they are losing sales but it hasn't happened yet...

The most frustrating part of trying to determine the voltage output is trawling through youtube 'reviews'. To me it's a basic parameter yet reviewers hardly ever mention it.
I like the look of this mod but as soon as i saw no voltage specs listed i dismissed it :(