12 inch round "cookie" and 11 inch round "filling". Thank-you themrsprinkls and sueognibene for your help! Also thank-you Fri-nite cake club for helping me with my issues as I was decorating! It is not as smooth as I would of like, but I had to take it all apart and stablize it-after I had finished 98% of the silly cake! Next time I would make sure there was at least a 2 inch differnce in filling size. TFL!