Wheel offsets, 172 cup

[Zippykya]

Thinking of buying some aftermarket wheels, I need to know what offsets are on 172 cup. I've noticed on previous threads that members stated that they are ET37, I've also been in touch with K-tec, but they claim that they are ET42??

Any help much appreciated.

Thanks

 

[Rich_16v]

172 Cup is ET38.5 100% definate
Normal 172 is ET42
Cupped 182 or Trophy is ET45