Although it isn't specified on the product page, the box lists it as compatible with the G10 and G11 as well as the G12. Unlike the old filter adaptor for the G10, this one telescopes as you zoom, so it doesn't cause vignetting on wide-angle shots. It's springloaded so it opens and closes automatically as you zoom, and the filter threads don't rotate so it's easy to use with a polarising filter.
It's made from plastic, and that includes the filter threads, so you need to be careful not to crossthread them. When fitted it extends 31-49mm further than the lens ring it replaces (W-T, no filter fitted). The outside diameter is 66mm, so it protrudes about 5mm below the base of the camera. That means you can't sit it flat on a table - the camera ends up tilted back slightly. It also obscures the optical viewfinder, almost covering the entire bottom half in wide, but as you zoom in it obscures a lot less and becomes a slight blur at the bottom left of the VF.
Overall I think I can put up with those niggles, because it's more compact than the non-telescoping designs and you don't have to mess around changing the adapter length when you zoom in and out.