Fisher Space M4 Series Pen Raw Brass – The new M4 Raw Brass Cap-O-Matic Space Pen features a stylishly rustic appearance, and each will develop its own patina pattern over time through use as well, making yours more and more unique to you as time goes on. Containing a Fisher Space Pen Pressurized Ink Refill Cartridge, the pen will write upside down – at any angle, under water, through grease, extreme temperatures (-30 to +250 degrees F), on almost any surface, three times longer than the average pen, and of course in the gravity free vacuum of space, and all are lifetime guaranteed for quality against all manufacturing defects – American Technology.