I just filled it up with Caran D'Ache Infinite Gray. It had just finished a bottle of Sailor Yama Dori, which took over a year to empty. I had been using it for a few days, went to take the cap off, and CRACK! Not sure if I want to replace it or just be done with TWSBI. I'm not a fan of mailing stuff. I gave the brand a fair shot. Loved everything else about the pen.