This is the standard refill for almost all Fisher Space Pens. It is supplied with a small plastic adapter that allows it to work in almost any pen that uses 'Parker-style' G2 refills. The pressurized refill features black ink with a medium point. It is reliable in zero gravity and extreme temperatures, writing better on damp, greasy, or dusty paper. It also performs well in freezing or excessively warm conditions and has a longer shelf life than standard ballpoints.