I present my pen refill adapter, for use in pens that take the Waterman type ballpoint refill. It allows such pens to use Uni UMR-109 refills (not included) or other similar 98-99mm long plastic tube type refills instead.
The Waterman Ballpoint refill is around 112mm long and 5.6mm in diameter. The Uni UMR-109 refill is around 99mm long and 3.1mm in diameter.
Other suitable refills include:
Ohto - G-95NP, No.99(X)NP
Pentel - BKSS7, BKSSN5, BXS(X), XBXST5, XLRNT5, XBGRN(X)
Pilot - BVRF-(X)
Uni - SXR-89-(XX), UMR-109-(XX)
Zebra - EK-(XX), NJK-(0.X)
I appreciate that these replacement refills are generally less practical refills, compared to the Waterman Ballpoint refill, in terms of ink volume. However, since the Waterman refill is a propriatary refill (although Monteverde do make a compatible pattern refill), these refills come in many more varieties of ink, from oil-based, to gel, emulsion and hydrid, which are not available in the Waterman Ballpoint refill size, so this adapter exists to hopefully provide flexibility, between your favourite pens and refills.
The adapter needs to be printed in the polished white or coloured plastics, as the smooth polished finish is functionally desirable. The refill is held in place, by the adapter, using friction. The holes around the side of the adapter are present to help with the removal of unbonded plastic powder from the core, when being polished. However, some powder may still need to be removed, with a pin or thin metal rod, before inserting the refill.
Due to the very varied nature of pen design, I cannot guarantee that this adapter will work with any specific pen, although I've made every effort to make it as universal as possible.
I plan to make as many refill types compatible with as many host pens as possible, so If you have any suggestions on refill adapters, please let me know and I can hopefully make it available, depending on the relative sizes involved. I have now created dimensioned drawings of over 80 standard and obscure ballpoint, gel and rollerball refill types, so I like to think that I have a fair idea of what is and isn't possible.