The rubber MagMod grip goes over the flash head, and the built-in magnets can then connect with the magnets in the Selens flash diffuser. Please see last three photos showing it being used with a flash (flash not included).
Both are in very good condition. No original packaging/manual (but pretty self-explanatory).
From a smoke free environment.
*** FREE Royal Mail Tracked 24 Delivery' ***
Will be VERY carefully packed!