insulation products made of irregularly shaped hollow glass fibers of the present invention may be produced from a rotary fiber forming and pack heat setting process as shown in fig1 two distinct molten glass compositions a glass and b glass are supplied from any suitable source of glass such as furnaces 10 and forehearths 12 to rotary fiberizers 14 as discussed more explicitly below the fiberizers form hollow dual component fibers preferably the glasses have different mechanical attributes so that upon cooling they will assume an irregular as opposed to straight configuration such different mechanical attributes may be for example differing coefficients of thermal expansion differing melting points differing viscosities or differing mechanical strengths veils 18 of hollow dual glass fibers such as irregularly shaped hollow glass fibers produced by the fiberizers 14 are collected on conveyor 16 as wool pack 20 by means of a vacuum positioned beneath the conveyor not shown as the fibers are blown downwardly by air or gases to conveyor 16 by means of blowers 22 adjacent the fiberizers 14 they attenuate cool and attain their irregular shape the wool pack 20 may then optionally be passed through oven 24 at heat setting temperatures of from about 700 u00b0 to 1100 u00b0 f 371 u00b0 to 593 u00b0 c the heat setting temperature may be achieved either by retarding the fiber cooling process after fiber forming to retain some of the heat from the fiber forming process or by reheating the fibers in heat setting oven 24 while passing through the oven wool pack 20 is shaped by top conveyor 26 and bottom conveyor 28 and by edge guides not shown while in oven 24 the glass fibers may be subjected to flows of hot gases to facilitate uniform heating when the fibers.