@Stopwatch1986 Ah, you’re right about the Safaris! Most cartridges are made to fit inside as many pens as possible, so there aren’t many that work that way. The way they fit is strong enough that it takes a fair amount of force to dislodge it, at which point I’d be more concerned about the state of the pen than if the cartridge has been knocked loose.
@Stopwatch1986 I’m sure there were/are some Parkers that did it too, now that I think about it