Hi Mate
A cylinder = b-piston
B cylinder = no mark piston
C cylinder = D piston
Or order from www.tyga-performance.com and just order by cylinder number but these bikes are getting old now and the cylinders may have been plated so the best is to messure the cylinders and send a e-mail to tyga with the size and they will send you the right pistons for your bore size .
While your mesuring the cylinders you can also check to make shore the cylinders a round .
That is if you have tools to do thay if not you could go to a local engineer and get them to check,mesure them .
Hope that helps