Yeah as Adam says I'm sure it'll be either 21mm or 23mm.

The Whiteline 24mm rear adjustable bar would be a good choice to go for though.

Damian @ DPM Performance
 
The standard front is 21". Ive upgraded to the 23" R32 one, and an adjustable 24" Whiteline on the rear.

Still running standard shock/springs and am impressed with how it handles.
 
I've got the Whiteline adjustable from Damian, set on hardest setting and I think its bang on. The body roll is kept much more in check, had a bit of fun oversteer but nothing OTT at all, just fun and deliberately induced :D