I bought the Grifiti Fat 12 from Grifiti's website… it’s a nice soft case. Fits my V60 much better than an Apple-super-duper-slim-keyboard case off Amazon did. When I get my FC660C I’m curious to see if it fits. Here’s some more dimension info from MD:
Grifiti Fat 12 - 12” Compact Keyboard Case dimensions - 13.5 x 6.25 in (34.29 x 15.88 cm)
Grifiti Fat 14 - 14” Tenkeyless Keyboard Case dimensions - 15.25 x 7.0 in (38.74 x 17.78 cm)
Grifiti Fat 17 - 17” Full Size Keyboard Case dimensions - 18.5 x 7.0 in (46.99 x 17.78 cm)
Now I measured my Fat 12 at 13” x 6” so these numbers may be generous...
Oh, also, the closure is just a neoprene “cap” that slides into place, so if you need a positive closure like velcro or a zipper, these ain’t it.
HTH