These Are Refills For Sea Gems Range Of Pens.
There are different types for different pens, to see which one you need simply ‘break’ your pen at the middle, the chrome bands usually denote where this point is. The refill is inside the bottom half, you may need to screw it out.
Some take a smaller size and so a pack of two refills is supplied for the same price as one larger cartridge.
By Sea Gems.