STANAG 30-round Magazine for WE13-3A / KS-1, KS-3 GBBR Replicas [Well Pro]

I have ordered 4 aditional magazines to have beside the one that came with my GBBR replica and so far they all work perfectly.
I only have one game with them, so about 4h of play time but there are no gas leaks and they perform as expected.
I am using a speedloader to fill them up with BBs, but there is also an alternative way to do it by removing the feeding tube and fill it up like a pistol magazine. I don't use this method because I can't see if the BBs are stacking nicely inside or not, but nevertheless it's an option.
It would be great if we can buy these feeding tubes separately, that way you can have a few of them already loaded with BBs and just switch them instead of refilling with BBs manually each time.
Overall I don't have any issues with these mags and I recommend them if you have a Wellpro GBBR rifle.