I'm actually ready to buy my next costlier brush. I have a Berkeley, Special, and Wee Scot. My sweet spot is the 18-20mm range. Your potential choices for me are:
Simpsons Keyhole 1
Simpsons 55
That is all. They are the right size, the right hair, and close to the same price.
Simpsons Keyhole 1
Simpsons 55
That is all. They are the right size, the right hair, and close to the same price.