I think he's asking about the wedge on the underside of the holster, as opposed to the Raven "claw" lever that facilitates the grip tuck. The JMCK and the Keepers both use a soft (neoprene?) foam wedge, whereas the Raven wedge appears to be hard plastic.
Looking at this style of holster, I'm imagining an amalgamation of features between this and my JMCK for an ultra low profile AIWB holster...