12 point spline tool

[Trevor Irwin]

'90 Audi 100 FWD
There are six bolts connecting the drive shaft to the tranny. They are
12-pt spline or triple-square things. Does anyone know what size they are
(its either 6mm or 8mm I think, but I'm not very sure how it's measured). 
I hope to find a place in town that carries the tool tommorow (no luck
today), but in case I don't, does anyone know where I can find one?
Thanks.

Trevor