Sensa

Sensa is a maker of comfortable grip pens that went out of business recently. Their fountain pens take a standard international ink cartridge or piston converter. Their older ballpoint pens can only take a Fisher Space Pen standard pressurized refill, while their newer ballpoint pens take any Parker style G2 refill. If your Fisher Space Pen refill came with the G2 adapter, you can use that refill with the newer Sensa ballpoint pens. Their rollerball pens take a Schmidt 8126 long capless rollerball refill. Note that the P8126 standard capless refill is too short.