Mystery busters: is ryobi that low quality thus will not suffice for real traides' needs?

Yes and no, for some 'power focuesd' tools like saws and grinders, every bit of the motor components counts, and all these add up to ensure the overall power and endurance, hence better stick to the mainstream brand like milwaukee, makita, etc.

But, for the non power oriented tools like a fan, a torch, a caulking gun(power achieved via gears not motor), even a jig saw (yes, a jigsaw, no matter which brands it comes from, will only have around 420w power, and that's all you need), ryobi is more than enough to get you around the work, plus offering you the best affordability. 

Not to mention there are a few tools that only can be found in ryobi's range, like the cordless hot glue gun...

So now, after a second thought, if you begin to wish to add 1 or 2 pieces ryobi tools into your tool box. This adaptor is for you, jump straight to the cheap affordable goodies, without spent any extra penny on their battery and charger and saves from carrying those around!

Disclaimer: all adaptors can only be used between your tools and batteries, they are not designed to be used with the charger. And logically if you got the charger, you should get the adaptor the other way around right? :)