RISER BLOCK... This spacer is designed to allow the Skimmer ground pod to accept the new Wimberley Head II, WH-200. (Because the pan knob is located to the side of the pan mechanism, more clearance is necessary than with the original Wimberley Head.) The RB-100 spacer is easy to install: simply screw the spacer onto the Skimmer. You can then attach the Wimberley Head II onto the spacer.