You should be able to source the parts to build a wheel from scratch for around the �450-500 mark (Talon hub, bearings, Excel rim, spoke set and machined spacers), a little more if you require a sprocket and brake disc. Add to that the cost of building (if you don't fancy taking it on yourself) which would be somewhere between �60 and �100, and you should be able to do it for not far off half the price OTR charge for a ready made rear wheel.

Contacting Talon is probably a good starting point. They will actually build a complete wheel for you if you so desired and it will still be considerably cheaper than OTR (for the same product).

This thread maybe of use to you as well: http://www.xt660.com/showthread.php?t=21607

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