I don't know for sure, but I suspect the internals of the G320 are the same as the G310 / G311 as all the specs are identical.
(G320 has an obviously different case, with splines for roller brake fitment)
It says "Prijs per stuk", which means 'per piece' although the image shows a set of 3 so I'm also not clear if they are sold as a set of three or individually.