The Phenolic G-10/FR4 round rod has an opaque natural color and meets United States Military Standard MIL-I-24768/27 specifications. Phenolic G-10/FR4 is a plastic laminate produced from a fiberglass that is impregnated with epoxy resin. Also called Garolite or epoxy grade, Phenolic G-10 provides high moisture resistance and good electrical insulation properties for electrical applications.

Plastic laminates are hard, dense materials made by applying heat and pressure to a series of layered paper, fabric, or fiberglass and then impregnating them with epoxy or resin. The most notable characteristics of plastic laminates are their moisture resistance, tensile strength, and typically good electrical insulating properties. Some grades also offer additional machinability. Moisture resistance describes the material's ability to resist moisture, which is important in electrical applications. Tensile strength, used to indicate the material’s overall strength, is the peak stress it can withstand before it breaks. Electrical insulating properties such as dielectric strength and arc resistance refer to the voltage the material can tolerate. Machinability is how easy the material is to machine while maintaining a good finish.