Look like these https://www.aussiestrength.com.au/premium-dumbbell-set-1470kg/
so its kg. 42kg dumbells aren't bad but looks like he is doing them from the floor so wouldn't be doing full range. Good for a 20 year old though thats for sure. Must have been pumping iron the entire time he was out with his foot.
Nephew of Andrew Vlahov if I remember correctly who is a mountain of a man