If it has a 15mm axle it'll be compatible. If it's 12mm it's not.

Easy peasy. Will check tomorrow morning

It should be compatible - worst case scenario with a different freehub. i recently looked to upgrade my old Powertap Pro+ but it has a 12mm axle and therefore did not work.

Sorry that's what i meant. Didn't want to order a new freehub to have to return it later

Yes it will be compatible. All the G3s are based on the 15 mm axle. The Shimano freehub has a spacer to convert between 10 and 11 speed. There is maybe a chance that it would have an older freehub body if someone swapped it out, but I am almost completely sure that these are Novatec freehubs. Much cheaper to pick those up off of Ebay.

I have an 11-speed cassette on my Powertap G3 hub. Which is for sale btw. ; )

gearing? I'll see about checking it out