I just bought a pair of Svt-40 magazines at $90 each from them and they were pretty much garbage. It says "may require fitting" on their website so I was expecting to do some filing, but they were awful, locking lugs are too far towards the top of the magazine, and stick out too far, the feeding ramp sticks up too high and prevents the bolt from closing, and the tab on the back of the magazine that is supposed to hold the bolt open barely sticks out at all and fails to hold the bolt open, and it is not part of the follower but is a lose part which complicates the design and causes the follower to stick. I got one of them to sorta fit into the gun (very tightly but workable) but it will not feed ammunition into the chamber as it doesn't hold them high enough.
I would try to return them, but I've marked them up trying to get them to work.
You'd be better off making your own magazine.