Regular masterlinks are secured with a spring clip that can be reused indefinitely as long as you don't damage it. There are quicklinks that are used mostly on derailleur chains that you are not supposed to reuse, but they are totally different animals from masterlinks.
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What, Me Worry? - Alfred E. Neuman
I'd like to think i have as much money as brains.
I see the light at the end of the tunnel, but the tunnel keeps getting longer - me