hair transplant, probably multiple? I heard the same about H&W on HTN. H&W are one of the best worldwide in FUT. He has a good haircut which gives a nice layering effect. Helps maintain illusion of density.
If you look closely on interviews, you can see his hairline/scalp is a little bit diffused but his haircut is just perfect for him to give the illusion of thickness.
Is Klopp taking finasteride though. He had a good hair transplant but looks like he's losing it behind that transplant. Needs a another now, replace what is lost. Seems he's not taking finasteride at all .
I don't know what's going on with him, at times it looks real and at other times like a wig. It could be a mix of a both.
I think it's impossible to get such good results from where he was before. He had very aggressive balding when young, pretty much lost everything on top aged just 25.