IIRC I tried some of those Korean Glock Magazines & they where Junk & got tossed out on the range & shot to pieces..
The SMG magazines cost $20 & the Glock 18 33rd ones cost around $30+
Don't go cheap IMO
The ones I just googled are different than the old ones = Gen 4/5 ambi mag catch
What type of device will these be used in? Kel-Tec Sub2000? AR-9 Platform?