My 2015 listed the medium size beads and that is what is on top a Corbin seat. Works well for me. The large size which is 14 x something was to big for the FJR seat but fit my 1400 ninja with a concourse seat.
I have the small one they designate as being for the pillion seat. It fits fine. You really only need it under your butt anyway; no benefit in having it hanging over the edges of the saddle.