dunno about regular hubs, but claimed 156g against the last iteration of the onyx hub.
The long anticipated Onyx Vesper has landed. The signature Onyx Racing Products sprag clutch hub is now available in a lighter and more easily adaptable format. The Vesper inherits the performance focused DNA of its predecessor without compromise. Significant revisions and tweaks on both the front and rear hubs result in a weight saving of around 156g depending on the configuration.
Gonna take a wait and see on reduced sprags and narrower contact patch.
The rear hub represents only a 65g weight savings. Not insignificant, but the front represents 49g. You could probably find a different front hub that's even lighter. I wouldn't go sellin yer hubs for 65g. In total it's 114g for the 32h 6b boost weights claimed.
I have a set that have been trouble free, but my mileage on them is low. Just swapped to an XD driver and cassette to drop some weight- it was an easy process and I managed not to fuck anything up.
Brief review- they are not light, especially with the steel shimano freehub, but it's not rotational weight and they truly do seem to spin very fast when coasting. The feeling of cruising through the woods on a silent bike is pretty amazing, hearing only the slap of the derailleur and the crush of twigs/small children...tho you may hear other annoying noises, like pivot creak and hose rattling so much clearer. Engagement is indeed very quick, but on my bike there has always been a minuscule amount of lash...as the system winds up from power. I can't really say whether I would prefer a lash-free high engagement style hub, or an instant engagement hub with some flex due to lash, but the silence of the onyx is worth it IMO.
I'm a pretty renowned cheapskate (@jonKranked ) but these were one of the few items I paid full price for on my bike build.