If I were only buying ONE spare, it would be another 6-rounder for concealment backup. I like lots of magazines and have 3-4 flush ones as well as 6-10 "high capacity" Kahr mags for spare carry and range use.
I try to cycle all of my mags through range use and use the ones without any problems for CCW.
Wynn
USAF Retired '88, NRA Life Member. Wife USAF Retired '96
Avatar: Wynn re-enlists his wife Desiree, circa 1988 Loring AFB, ME. 42nd BMW, Heavy (SAC) B-52G's
Frédéric Bastiat’s essay, The Law: http://mises.org/books/thelaw.pdf
Thomas Jefferson said
“A government big enough to give you everything you want, is strong enough to take everything you have.”
and
"Peace is that brief glorious moment in history when everybody stands around reloading".