This attachment piece is made for our efin V2 to attach it to a standard fin box. We have had a few customers that have damaged their efin where the center fin bolt or where the pin goes into the fin. This piece can be attached to your efin with some modification.  Drill holes in the base of the efin, and cut away the D shape fitting on the attachment. Use Stainless Steel bolts with lock nuts to attach the piece to your efin.