DeepColdWaterAccording to the Well Appointed Desk, any of the following refills work for a pen that uses the G2 refill:
G2/Schmidt/Euro Rollerball (and similar) Refills:
The Pilot G2 style refill, also described as the Schmidt/Euro Rollerball refill size are about 110mm long:
Caran d’Ache Fibre Tip Refill
Caran d’Ache Rollerball Refill
Faber-Castell Rollerball Pen Refill
Faber-Castell Fineliner Pen Refill
FORAY (Office Depot) Pen Refill For Schmidt Rollerball
Kaweco “soul” refill G2
Kaweco G2 Gel Roller Pen Refill
Hi-Tec-C Cavalier refill
Monteverde Fineliner Refill G52
Monteverde Ceramic Rollerball Refill W22
Monteverde Spring-Loaded Tip Fineliner Refill G62
OHTO Ceramic Rollerball Pen Refill
OHTO F-300 Fude Refill Black
Pentel LR7 Energel
Pilot Frixion Erasable Gel
Pilot Juice (removed from plastic retractable pen)
Pilot G2
Pilot LP2RF Gel Refill (Juice refill code)
Schmidt Capless Rollerball 8126 and 8127 (shorter models can work with an extension hack)
Schmidt FineLiner refill
Schmidt Safety Rollingball Ceramic refill
Schmidt Safety Rolling Tube refill
Schmidt RollingSupersteel refill
Schmidt RollingBall refill
Schneider Topball 850 Pen Refill
Schneider Topliner 970 Pen Refill
Sheaffer Fineliner Refill
Visconti Rollerball Pen Refill AA40 0.7
Zebra JT refill
Zebra Sarasa Clip refill (removed from plastic retractable pen)
http://www.wellappointeddesk.com/2014/06/the-epic-refill-reference-guide-rollerball-gel-and-ballpoints/
G2/Schmidt/Euro Rollerball (and similar) Refills:
The Pilot G2 style refill, also described as the Schmidt/Euro Rollerball refill size are about 110mm long:
Caran d’Ache Fibre Tip Refill Caran d’Ache Rollerball Refill Faber-Castell Rollerball Pen Refill Faber-Castell Fineliner Pen Refill FORAY (Office Depot) Pen Refill For Schmidt Rollerball Kaweco “soul” refill G2 Kaweco G2 Gel Roller Pen Refill Hi-Tec-C Cavalier refill Monteverde Fineliner Refill G52 Monteverde Ceramic Rollerball Refill W22 Monteverde Spring-Loaded Tip Fineliner Refill G62 OHTO Ceramic Rollerball Pen Refill OHTO F-300 Fude Refill Black Pentel LR7 Energel Pilot Frixion Erasable Gel Pilot Juice (removed from plastic retractable pen) Pilot G2 Pilot LP2RF Gel Refill (Juice refill code) Schmidt Capless Rollerball 8126 and 8127 (shorter models can work with an extension hack) Schmidt FineLiner refill Schmidt Safety Rollingball Ceramic refill Schmidt Safety Rolling Tube refill Schmidt RollingSupersteel refill Schmidt RollingBall refill Schneider Topball 850 Pen Refill Schneider Topliner 970 Pen Refill Sheaffer Fineliner Refill Visconti Rollerball Pen Refill AA40 0.7 Zebra JT refill Zebra Sarasa Clip refill (removed from plastic retractable pen)
http://www.wellappointeddesk.com/2014/06/the-epic-refill-reference-guide-rollerball-gel-and-ballpoints/