I received two inserts - one for Unibody MacBook Pro and one for 13" white MacBook Pro. Nothing for MacBook Pro with Retina display, but no loss as I don't have one.
The unibody insert does not "fit like glove" and in fact, sitting horizontally, my unibody Pro leans sideways a bit. Further, cable management with my 15" Pro is worthless. It is not possible to place the MacBook Pro into the stand vertically as the arc blocks both the power connector and the Ethernet port. Plus, given the fit, this seems a bit high risk anyway. Horizontally, it works and does free desk space, but no cable management.