The PFM thumb brake master cylinder, is full a professional race spec master cylinder - if you want the very best money can buy, then you have found it.
Utilising the same high energy piston actuation system used for the front master cylinders, a three sealed ball bearing system allows the piston to travel in a parallel fashion to the cylinder bore with minimal side loads, stiction, seal compression or extension. The end result is a superbly smooth and easy actuation, resulting in more brake line pressure (braking power) with less effort on the lever and less rider hand fatigue.