Countless experiments and a common sense approach to findings resulted in the invention of the sealed and pressurized Fisher Space Pen and in 1967, after 18 months of rigorous testing by NASA, the Space Pen was selected for use by astronauts. The Q4 is a multi-use pen incorporating a black and red ballpoint, a pencil and a PDA stylus. It uses an ultra hard tungsten carbide ball and thixotropic ink in a hermetically sealed, pressurized reservoir which will last three times longer than a conventional refill.