Glock factory mags are the way to go - Glock MF10017 Magazine G17/34 9mm 10 Round Black Finish Packaged

OP's price on these was decent, and THEY HAD THEM IN STOCK. Have been using glock OEM mags in USPSA matches for a year, and zero failures. These cost more than the copies, but I have not had any fail, unlike some cheaper copies from a brand that begins with "M". Also, you can order EVERY component of a mag (with exception of the main body housing) directly from the Glock website, so if a part breaks or springs get fatigued, the parts can be replaced very cheaply to keep the mag running forever.