JOM Exhausts!

[VDUB-Polo]

I drive a 2005 VW Polo 9n3 MK 7 and i need to know the size of back box i'll need. JOM gives three options respectively for the MK 7 Polo;

-76mm
-90mm
-100mm

http://www.venommotorsport.com/manufact ... o%20Mk%207

Please could someone tell me what size i'd be looking at buying, i presume that the different sizes relate to the size of the pipe traveling to the original back box.

Has anyone with a 9N3 changed their exhaust??
Please help.

Cheers