IMHO, don't be cheap and don't buy the cheapest you can. Quality mags may cost more, but are well worth the added expense.
I purchased some surplus mags once. By the time I got through the garbage mags, the only good one left cost me the same price as buying 1 good quality mag to start with.
(I think I know what I said, but the bottom line is "BUY QUALITY MAGS")
"A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."
Life Member NRA
Life Member NAHC
Former President of the ECPT