The unusual design of the Rocket Pen comes from the custom knife maker Darriel Caston. You not only see the oval cross section of the tactical pen right away, it also feels very pleasant to hold. Made from black anodized aluminum, the Rocket Pen is not just a capable tactical pen, but also an elegant writing tool. The bayonet mechanism with lateral slider is skillfully integrated into the line. The diameter is 8.3 / 11.3 mm. Compatible to Fisher Space Pen Refill #PR4 and Parker-style refills. To refill, loosen the T8 Torx screw at the end of the handle.