Here we have a brand new AJP/Braktec rear brake master cyclinder to fit the following bikes:
Montesa 4RT (2005 Onwards) Montesa/Honda part number 43500-NN4-K11
Montesa Cota (315R 2001 to 2004) Montesa / Honda part number 43500-NN3-830 
Scorpa SY250  (2001 to 2008) Scorpa Part number S1A-40601-00-00
TRS One  (2016 Onwards) TRS Part number 70305
It has 40mm bolt hole centres and is in a dark grey finish.