Wipperman says they're re-usable....but dirty secret, many many of us open/close KMC links that cost 6X less each once or twice over the life of a chain. Yes, we're terrible human beings that are probably going to die horrid deaths.
Buy a 6-pack, leave one always in your tool bottle/bag. Since chains became non-pinnable in the field without peening, I haven't left home without at least one link-set.
https://www.amazon.com/KMC-Missing-s.../dp/B01G9RYY5O