Abstract: A radially expansible supporting collet for a tubular light-weight sleeve upon which a continuous filament, yarn, or roving may be wound. The collet comprises a plurality of axially extending, sleeve contacting bars carried on a generally cylindrical body which is rotated on its normal axis. At least one generally annular, closed, pneumatically expansible bladder is carried by and rotates with the body. The bladder is located inwardly of the bars and may be connected to a source of air under pressure. When the bladder is expanded by the air, it presses outwardly against the bars to move them radially outwardly against the interior of the sleeve in order to hold the sleeve concentric with the axis of the body, to prevent its axial movement and to transmit torque to the sleeve.