Once you soak this brush in hot water, it REALLY opens up and only then do you get an idea of just how large this brush is. While it may only be a 24MM knot, because it is so dense, it acts like a 26mm shavemac. Although it is large, it is by no means unweildly or hard to control, and its density and size still allow for one to "build up" lather on your face, and control the application of lather. It is much larger than its brother, the PJ2 (see pictures below) and as a result does not have the light/agile feel of the PJ2, however the greater size allows for a more luxurious feel. It did a simply splendid job at whipping up a superb lather with salter mint - this brush is certainly a keeper. Like every simpson I have owned - it did not lose so much as a single hair in its maiden voyage.