Ohto G-307 Gel Ink Pen Refill - 0.7 mm - Blue Black

I have purchased three of these with poor performance upon receipt. JetPens provided technical assistance immediatly to fix the problem.

The only issue is incomplete lines. As if the roller ball was sticking or the flow of ink was stalled. This was more pronoun on scientific notebook use. It did perform if the length of time on paper was short and the paper was thick.
If I could get this thing to work it would be perfect. I love the color and line when it works.

End result = a bit of frustration and ~$20 down the drain.

After trying this 0.5 black Gel refill for the Ohto pen it is now my favorite. Until I discovered Jetpens I had been using the Uni-ball 207 0.5 (micro) cartridges (scavenged from 207 RT pen donors) in my Ohto pens. The G-305 produces a slightly darker black than the Uni 207's. Otherwise the performance is similar and the sealed metal cartridge is a plus compared to the plastic 207's. The only reason I would not use these would be cost as you can get a two pack of the Uni 207 Rt's for about $3 vs $5 each for the Ohto Gels.

The G-307 gel ink cartridge is the way to go! Very smooth and never skips like the C-307 cartridges have a tendency to do. Might be the perfect ink cartridge, and I've been searching for that for a long time. The G-307 is smooth in a controlled way for a .7mm cartridge, and doesn't get sloppy the way the Parker Gel Ink refills can get. Only issue might be how long they last and whether or not they begin to write differently towards the end of their capacity. Will keep you posted. Makes my Orcas the perfect pens!

This is currently my absolute favorite ink replacement cartridge. It's silky smooth and doesn't ever skip. The Pentel KLR7 and LR7-A cartridges are solid as is the Pilot BLS-G2 and Zebra JF 0.7. I've even gone to some of the higher-end Waterman, Lamy (M66, M63), and Mont Blanc rollerball cartridges and none are as good as this cartridge. I've tried well over 100 different ink cartridges over the past year and THIS is the one that I use every single day. Highest possible rating.