A review of spinneret designs for melt extrusion systems focuses on plate sizes, raw materials, bore hole shapes, and future trends for increased performance. During typical extrusion operations, spinnerets accommodate temperatures that range from 200 to 400 degres centigrade and mechanical pressure loads that range from 30 to 400 bars. Consequently, most spinneret plates are made from corrosion resistant stainless steel. A table lists industry specifications for various types of raw steels, including ferritic, austenitic, and precipitation hardened. The manufacture of spinnerets is accompanied by continuous quality control monitoring, including microscopic inspection, caliber gage, air flow, and oil viscosity flow tests. The oil viscosity test employs the Hagen-Poisseuille formula to measure the pressure drop per bore hole for a defined fluid stream of high viscosity. A diagram portrays the cross sections of shaped capillaries and counterbores for specialized end uses.