Unless you have a select fire option, I don’t really see the point of using a 50 round aftermarket drum mag. I’ve seen sporadic reliability issues with them in reviews, but even if they were completely reliable they have limited use or appeal, in my view. I have a few OEM 33 round 9mm magazines for GLOCKs. I can’t tell you how often I’ve loaded them for people only to watch them fatigue trying to shoot 33 rounds uninterrupted. Perhaps there is some merit to having a lot of ammo at the ready should the rule of law break down, but aside from that, it doesn’t seem like money well spent.
If you buy one, I hope it serves you well.