Concave Ribs are detachable fins used in the Detachable Fin Mold. Now with three types of fins available. Each style has a set of 24 ribs or fins that can be arranged to meet your specific needs.
Concave Ribs (product you are viewing)
Small Concave Ribs
Interchangeable on the Jim Moore Detachable Fin Mold base.
PDF of Interchangeable Rib Sizes