The 729s are Mavic's top line extreme use disc rims, using a super broad 36mm single box extrusion for as near bombproof performance as you'll get without stupidly excessive weight. The wide rim bed means even 3in tyres will sit nice and square on it too, with anything from 2.3-2.5in wide getting a real stability boost from the broad base.
The spokes are good strength and support and overall build quality is good and tight with no bagginess or flex during or after testing. Yet again, Hope's new Pro II hubs proved totally trouble free. While it seems odd to see them in such a burly build up, they're compatible with all axles from QR to bolt through front and rear, and Hope assure us that they're both stronger and stiffer than the old BULB hub they replace. However, Pro Build pricing isn't as good identical wheels from mail order suppliers.