It's a basic thing really - and yet so essential if you're planning on using cartridges with your Pilot Capless pens. I'm pretty certain you get one with every type (Decimo, VP and Fermo) but it never hurts to have a spare (or in my case - 3 or 4). The converters for these pens lack capacity - which is unfortunate because I honestly believe these are some of the best pens for work. A cartridge solves that. Whether refilling or using a fresh one, you need a cap to protect the cartridge. If you have a Pilot Capless have Goulet throw one in your next order. They work beautifully in all three types of Pilot Capless pens.