1 oz. copper (0.0014") on a 1/16" (UL 94V-O) epoxy-glass FR-4 board. New high quality positive pre-sensitized PC boards are double protected from light and handling damage and feature copper on one side only. The peel-off coating protects the board while handling or cutting prior to exposure. Can be exposed with common fluorescent lamps. GC makes it easy for anyone to make a professional looking board. Use with GC Developer Part Nos. 22-225 or 22-226 mixed 1 to 9 with water. Dielectric constant at 1 MHz = 5.4.