In reply to henwardian:
the super light rocks have always been 6kn above the smaller sizes, the only change is the old ones size 1 and 2 are rated at 4kn and the new ones only size 1 at 4kn.
The reason I stopped using my super light rocks is for a few grams I don't think cutting the safety margin down to 6kn is worth it. I think for a nut to be almost impossible to break single pitch trad climbing it needs to be atleast 8kn and possibly 9kn. Also bare in mind on multi pitch belay anchors are unlikely to be evenly loaded and you may need stronger gear still in the case of a factor two fall on to the belay.
Apparently there used to be a lot of gate open biner failures when most of them were rated under 7/8 kn gate open but now we see much fewer as they are able to handle this.
Post edited at 15:23