Originally Posted by Opinionated
GunBroker listings are cagey about listing the magazine capacity so one must assume that they are the 10 round until and unless further information is forthcoming.
I would think it would be the opposite: Unless otherwise stated, I would assume they are the standard 15-round mags.
15 is the standard magazine capacity. Most states don't arbitrarily place artificial limits on magazine capacity, so most of the guns Glock ships come with the normal mags.
I'm guessing most Gunbroker listings are "cagey" about listing magazine capacity for Glock 20s because the normal capacity mags are 15 and they don't feel the need to post that. I know in my state we don't really think about the fact that some Glocks come with neutered mags; if someone says "Glock 20 magazine" I automatically assume it has 15 rounds.