Uni-ball Signo DX UMR-1 REFILL for UM-151 ULTRA-FINE LINE-12 Pcs-0.38mm Ball(Black) Refill for Uni-Ball Signo UM-151 Gel Ink Pen Black Ink 0.38mm Ball Clean, precise line all the time Perfect for extremely fine writing Smear-proof bio-polymer ink prevents feathering. Attached with Dbmier A750 Mini Notebook.