The OCR rims have the spoke holes drilled with an off-set, i.e. not centered on the rim. The offset is to the non drive side which allows the rear wheel to be built with less "dish" compensating for the cassette width on the drive side.
The Ritchey "zero" offset rear hubs allow for a zero dish build with equal spoke length and tension both drive and non drive side. CRC stock Ritchey zero WCS hubs and at 30 odd squids for the hub it is a very light and trick rear set-up for the $$.
Enjoy!!