The master cylinder that Sylva supplies for a Riot originates from a Caterham 7. It is Girling part number 74066147. I am led to believe that is has an 11/16", 17.46 mm bore. Since driving the latest Sylva demonstrator, which is fitted with a Willwood 1" bore master cylinder, I'm keen to increase the master cylinder size as I really liked the feel of the brake pedal. I could just fit the Willwood cylinder, but this means modifying the pedal box, something I'm not keen to do. 

I noticed that Caterham supply a 13/16" 20.64 mm bore master cylinder made by AP racing, part number 77176. From the picture below you can just make out that it even has an SVA compliant cap.

The standard master cylinder has an affective bore area of 239.42 and the AP product, 334.63. That is an increase of almost 40%. Sounds perfect! Problem is it is £164.50!