I have only ever used Mason Pearson brushes on my hair. As a small child my mother used this exact brush, it was hers when she was younger and she brushed my hair with it until I was about 6, then she bought the larger version for me which I used until I was about 20. Then I bought one this size again as its more portable and 15 years later it is still going strong.

This brush is expensive, infact I was shocked to see how expensive! I think I paid about £25 for my last one, the junior, with the cleaning brush to go with it (you can also get it without) although sadly I'm not sure what I've done with the cleaning brush, I think it got lost in a move.
The brush head is 3in long by about 1 1/2in wide at the widest point. The black bristles are boar bristle (eew!), which I didn't know until now, the white bristles are nylon. Each "clump" of bristles in the head of the brush are made of a couple of longer nylon bristles surrounded by a larger amount of the thinner boar bristles which are shorter. The bristles are placed in a rubber pad which helps airate the hair as you brush it.

When I had the cleaner brush I used it to remove the hairs from the brush which is really useful, since losing it I have to do it manually which doesn't work as well. I wouldn't suggest washing the brush, I did this with the large version I had and eventually it caused the rubber pad to come unstuck from the plastic brush base, although I did super glue it back together and recently I discovered my father now uses it!
The plastic base and handle of the brush is really strong and after 15 years only has a few scratches on it. The handle is a good shape and size and comfortable to hold.

Conclusion
It's expensive but very good, especially for thick long hair - it doesn't pull. This is the best quality brand of brushes I have ever come across, very well made and extremely long lasting. I give it 4/5 it's brilliant but I was very shocked how expensive it is now, really glad it lasts so long, and will certainly be looking after the one I've got.