Chris,
have a look at the homologation tag on the kart.
it should be on the rear bar, behind the seat, in front of the axle.
It will have a model and an expiry for the homologation.
The kart may be upto 6 years older than that. Anything from ’03 to ’05 (which would be my best guess) is going to be essentially the same.
It’s either a 2004 or 2005 Kosmic T8. Primarily 32 mm, with the “B-Tech” system OTK used on that generation of chassis where one tube can be both 30, and 32 mm.