The chassis was made of extruded and formed 6061 aluminum. Rubber may then be extruded or molded before being cured. The body was custom fabricated from extruded aluminium by Coventry Steel Caravans. Copper is less ductile than aluminium, so it cannot be extruded into heat sinks. Nylon resins can be extruded into rods, tubes and sheets. Synthetic fibers are generally extruded in continuous strands of gel-state materials. The two major types of base construction are extruded and sintered. Polyester is extruded from polymers derived from natural gas and oil. The polymer solidifies by cooling after being extruded from the spinneret. These were extruded into cylindrical slugs, and then canned. Rubber fenders are either extruded or made in a mold. POM is commonly extruded as continuous lengths of round or rectangular section. Fiber can be made from extruded casein. Incense mixtures can be extruded or pressed into shapes. Excess material is extruded on the ground surface, forming a faecal casting.