ZAGE are poor quality along with Mementum Turbo and Forced Performance.
All knock off from Taiwan
I looked into it myself and not a good word said about them over the wate on the US Forums.
Speak to Harvey at
http://www.harveyperformance.co.uk he can do a 18G for £575.
I am currently speaking with Harvey about one for myself, just waiting for a few more questions to be answered.