Organic and glass filaments, yarns and/or strands are combined, with the organic component as the core and the glass component as the overwrap, followed by a treatment which causes the organic to shrink, causing spaced portions of the glass component to move or to tend to move radially outwardly with respect to the longitudinal axis of the combined structure and whereby, when the combined structure is in an elastomeric matrix, the region of the matrix contiguous to the organic component is in a state of compression while the glass component exhibits greater anchoring potential with the elastomeric matrix.
