28 are located outside the perimeter of backhole 29 sheath polymer streams from holes 27 in boundary plate 14 flow into the corners of star holes 28 because the bottom surface of boundary plate 14 confines the streams to star holes 28 the sheath streams flow laterally into the backhole 29 therefore boundary plate 14 forms the lower boundary for channel 24 and the upper boundary for star hole 28 the core polymer stream from hole 26 of plate 14 flows into the center of star hole 28 and down into backhole 29 where it is surrounded by sheath streams the combined flow issues from spinning orifices 30 to form round bicomponent fibers as will be recognized by the ordinarily skilled molten polymers may be fed to the assembly by any suitable conventional means molten core polymer enters the assembly through polymer inlet 17 shown in the elevational cross section of fig2 inlet 17 splits into feed legs 31 and 32 which feed the two main distribution channels 20 molten sheath polymer enters through inlet 18 shown in the elevational cross section of fig3 and flows to main distribution channel 21 fig7 further illustrates the general principle of the present invention shown in fig7 are three plates of a spin pack in partial cross section these plates illustrate the boundary pattern plate concept as shown plates 111 and 112 are boundary plates and plate 113 is a pattern plate polymer flow is in the direction of arrows p polymer passes through the cut through portion through.