Medium-point Fisher Space Pen pressurized refill. Standard refill fits most Fisher pens, and lasts 3 ½ times longer than typical ballpoint refills. With a Fisher Space Pen using this refill, you can 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.