PC-ABS (Polycarbonate Acrylonitrile Butadiene Styrene Blend) is ABS (see above) with some PC added to it. The primary reason is that ABS will burn, whereas PC is self-extinguishing. Blending the two makes for a flame-retardant material that meets Underwriters Laboratories (UL) flammability ratings, most importantly UL94-V0 which is often required in hospitals and other high-traffic areas. The PC also adds stiffness and higher temperature resistance. However, it is more expensive and mostly used when flammability is an issue.