A rotatable mandrel for holding a tube on which a glass strand is wound into a package which has elongated fingers extending lengthwise of the mandrel in closely adjoining relation, said fingers being loosely held for outward movement under the centrifugal force of the rotation of the mandrel whereby the tube is held to its greatest diameter, each of said fingers having a groove along its longitudinal center line and tapered edges whereby on termination of the rotating movement of the mandrel and of the associated application of centrifugal force against the tube, the tube is constricted by the tension of the wound strand thereon and to effect an accommodating reduction in diameter, portions of the tube collapse and enter into the depressed areas of the center grooves and tapered edges of the fingers.