I don't agree with Rolf Wacker's answer. I am a UW photographer and the GoPro is with me the whole dive so that I have MORE information, also for scientific purposes. The inserts are very practical. As for the size: it doesn't matter! If necessary, bend them once and push them down clearly with tweezers, far enough away from the O-ring -- otherwise it is not difficult at all to flood the GoPro with the anti-fog inserts!
I'm a really good customer of digital and buy a lot here, but whether it's 10 or 12, I can't remember, it doesn't matter, they're too expensive from any supplier -- that's the one item you're better off buying from AliExpress. Bought hundreds for a pittance! Made over 70 TG in Palau this summer, GoPro stayed fart dry.
You can forget them anyway, from the 6 series onwards they no longer fit into the housing. You don't need them there either, just set the automatic switch-off mode so that it doesn't get too warm.