Got my Glock Mags from Summit Gun Broker and tried them out. I bought G17 used mags and have to say, two of the three didn't look like they had ever been in a gun. One had some scuff marks on the base. All three worked perfectly. I can recommend them to anyone. http://www.summitgunbroker.com/
I send an Email to Mark Kitterman via the "contact us" link on the left side of the page. (third item down) and tell him what I want. He answers with in stock or not. Mags are 8.00 per order shipping for however many you order. Firearms are easy, too. Follow directions on "How to Buy" link. Second item down on left. I send a personal check (payable to Summit Gun Broker LLC) for the amount plus shipping via certified mail to:
Summit Gun Broker
PO Box 526
Grain Valley, MO 64029-9587
I get answers in the evening usually. and if you can email back quickly you will get a quick return email. Be sure to send a copy of the email or a detailed explanation of the item with shipping info with check. Write the item in the 'FOR' area of your check. (Ex: 3 used G17 mags) I have purchased firearms, ammo and mags and have had no problems when doing business with him.