Abstract: A novel spinner, for fiberizing hollow, irregularly-shaped insulating fibers is the subject matter of the present invention. The spinner is unique in a sense that its hole/slot pattern can be done by some standard drilling/milling techniques, which lower the cost of manufacturing. The invention uses two molten glasses (A and B) of different coefficients of thermal expansion, which are moved outwardly around the corresponding gas orifices by centrifugal force in a spinner pot. A stream of pressurized combustion gases is thrust through these central gas orifices to produce a hollow, non collapsible fiber of irregular shape. Molten glass A is introduced from the bottom of the spinner, and molten glass B is introduced above an uppermost flange and by means of centrifugal force, the two glasses A and B are forced upwardly and downwardly, respectively, into fiberizing centers.