Pilot Refillable 'Converter' Cartridge

For those unfamiliar with a 'converter', these Pilot cartridges can be refilled from any suitable fountain pen ink bottle. This means not only that you can choose from an endless selection of coloured ink, across brands, but also that you will never again depend on buying another cartridge. Indeed this refilling method is far more economical - but bear in mind that it can be more messy and probably a better option when not on the go. 

CON-40, the shorter of the pair, is suitable for the following fountain pens:
Capless "Vanishing Point" Fountain pens (in black, blue, red or yellow)
"Elite" Pocket Fountain Pen
To refill CON-40, dip it under the surface line of the ink bottle and screw until the cartridge has filled up completely. 

CON-70 holds a more generous amount of ink and will fit in longer barrelled Pilot fountain pens:
Custom 74 range with Fine, Medium, Broad or Soft Fine Nib
Custom 743 with FA Flex nib
To refill CON-70, dip it under the the surface line of the ink bottle and push the black button repeatedly until full.