I received this RazoRock 400 the other day. I'm not a fan of Synthetic Knots. So, when I ordered the brush, I also ordered a Whipped Dog High Mountain Badger Knot, knowing I would swap the knots. Before the operation. After 5 minutes in a Vegetable steamer. The hairs separated from the plug inside. No saving the knot. At first, I held it for 5-10 minutes in front of the vent, which gave it a good steam, but it didn't show signs of loosening. So, into the steamer basket it went. I will next have to meticulously dremel the glue plug out, and try not to mare the finish. If anyone else has ideas, I am open to suggestions.