Less temprature-sensitive visco-elastic foam and Polyurethane Gel.. Give consistent firmness for all night comfort. Gel-memory(polyurethane) pillows are designed for short-term cushion comfort. Pressure points of pain are created by body load force resisting the force of the foam. Visco-elastic pillows absorb impact energy by forming to contours. But they are temprature sensitive. Giving less support as Time passes. The SI-Tack alnite Gel-foam pillow is less -temperature sensitive then conventional visco-elastic foam pillows. Providing all night firm support for miximum relief of pressure point pain. All conture-shape pillows help align the body spines straightly, but only Alnite pillow provides consistent firmness for all night support and pressure relief. Polyurethane foam is mainly meant for cushion effect. It may provide confort for a limitws amount of time, but pressure points will soon be created as the resilient force of the foam resisting against the body load force. Visco-elastic(memory)foam is conventionlly temprature sensitive. It is excellent for impact energy absorbption. When the foam responses to the body heat, it becomes soft and molds around the neck to give comfort. But, It lose the firm support needed. SI-Tack Alnite pillow is made of an improved version of visco-elastic foam, Ie. The new generation memory foam. It is less temperature sensitive so that it will not respond to the body heat and become soft. Therefore, it could provide all night firm support to the neck while maimtaining the excellent impact energy absorption characteristic. "Chiropracticians' choice for all night neck support and pressure relief"