This paper expands Winnicott's “quantitative” definition of a “good enough” mother in qualitative directions, incorporating Bion's concept of maternal reverie, Bick's of the containing skin and the move from unintegrated to integrated states of being, and Meltzer's of two-dimensional states. These concepts are illustrated through two infant observation cases and one analytic case of a mother with a new baby. All are concerned with the nature of “fit” between mother and baby, and with the baby-within-the-mother; with the way reawakened infantile feelings can interfere with reverie; with the complications of mourning (in two cases); with the baby's struggle to introject the good breast whilst partly relying on second-skin support (in one case), and with the mystery of internalization in which (in another case) the thumb can take on the significance not of a mere plaything or transitional object, but rather, become the “agent of an internalized object in advance of the baby's conscious control”.