I have a Razorock Barber Handle brush with a 24 mm synthetic knot. I really like the handle but don't care for the synthetic bristles so I am changing it to a standard 2-band badger from Maggard's. I did watch a few videos on how to do this and some videos were certainly better than others. In any case, I have never done this before so wish me luck! I'll let you know how it turns out and I might even include a picture or two.