One black 0.3 mm gel ink refill for the Pentel Slicci Techo mini gel ink pen. We love this refill because it is able to replace many scratchy ballpoints with smooth operating gel ink.
For the Midori: snip the end of the cartridge so it fits into the barrel. Throw out the spring.
For the Sierra: snip the end of the cartridge and shorten the spring with wirecutters.