Fisher Space Pen refills use Fisher's patented refill system featuring a thixotropic ink which is forced from the refill by a pressurised nitrogen gas plug. This gives superior ink flow and writing at any angle and over adverse surfaces e.g. wet, greasy or very glossy.
Although primarily intended for use with Fisher's Space pens the universal mini pen refill snaps to length fits many pens and the standard space pen refill is supplied with an adaptor to fit pens that take a standard Parker type ballpoint pen refill.