First, do you mean a Voltbike BRAVO, or a bike I'm not familiar with? I'll go out on a limb and think since you're in Canada you mean Voltbike Bravo. They are out of B.C.
Second, I would think what's more important is the seat tube opening diameter? Is this what you're looking for? This will determine what seat post size you buy and if a shim will be required.
I'm thinking the seat rail size is not important. The seat mount adjustment on top of a seat post is widely adjustable to accommodate any number of seats.
Why not ask owners here in the Voltbike sub-forum what seat post fits the bike you're expecting?
