Matt here is a copy of an e-mail I recieved from Gianelli regarding GPR exhaust, this company is based in the U.K. but as I said can be obtained through Cycle Imports - talk to Ozy, also good contact for other GPR goodies.
The Derbi GPR 50 system - 33911 and 33912 are not in stock at the moment.
These are already on order with the factory and are expected in the next 10
to 12 days. The 33912 silencer is a carbon/Kevlar outer can. The 33917 is an
aluminium silencer which we do not stock and would have to obtain by special
The main expansion box is in mild steel with clear lacquered finish.
Price of the system with either silencer is