The Geib model has the same inside diameter as the Helleberg SH-II with a modified rim contour. The Geib cup is more bowl-shaped and slightly shallower than the SH-II. The entrance to the throat is tighter yet it shares the same throat size as the SH-II with a standard backbore. - the manufacturer California Residents Only: WARNING: Cancer and Reproductive Harm - www.p65warnings.ca.gov