Silky Geib Although it's said to be for rotary horns, I think it also suits piston horns (in my personal opinion). See below for specifications. I also purchased this used, so I'm offering it at a reasonable price. ● Geib Inner rim diameter: 32.76mm Throat diameter: 7.93mm Shank: American shank While it has the same inner diameter as the Helleberg II, the rim is more defined. The biggest difference is the cup; the Geib is more bowl-shaped and slightly shallower than the Helleberg II. The throat entrance is slightly tighter.