MG Chemicals 600 Series Positive Presensitized Copper Clad Board with 1 oz Copper This flame retardant laminate is translucent in color and made of continuous woven glass cloth impregnated with epoxy resin The copper on 1 ounce boards is 1.34mil thick (0.0341mm, 34.1 microns) The boards are made of FR4 which is a flame retardant version of G-10 material Developed specifically for the circuit processing industries requirements Complies with UL #E214381 (select boards comply to UL #E213990)