One of the very earliest printing filaments. Acrylonitrile Butadiene Styrene is still widely used for its high glass transition temperature (softening point) around 105ºC. You need to print ABS on a heated bed from 80ºC-110ºC, in a well-ventilated room and preferably in an enclosed 3D printing chamber (sides and lid) as it is prone to warping and delaminating (layer separation). Though it does give excellent fine detailed prints, strong and durable. Commonly referred to as Lego plastic.