Abstract: A flangeless winding core for magnetic tape, adapted for stacking between like winding cores, has an annular body with parallel top and bottom annular surfaces, an outer circumferential surface around which the tape is wound, and an inner circumferential surface from which a plurality of angularly spaced lugs extend radially inward, the inner ends of which are curved to define a discontinuous inner circumferential core surface. The lugs have the shape of a sector of an annulus, are spaced from each other by a like number of similarly shaped gaps, and project equally above the top and bottom surfaces of the annular body a distance greater than one-half the axial dimension of the annular body.