2 layer board of 0.50x0.87 inches (12.70x22.10 mm). Pierce Oscillator to generate a square wave from a crystal - see here or here for the theory. Board works with 3.2x2.5mm, 2.1x1.2mm or HC/49 through-hole crystals. Voltage range will depend on IC, e.g. this will accept 2 - 6V. R3/L1 are just there to show power is present.