The Uni UMR-109 Style Fit Gel Pen Refills are compatible with the Uni Style Fit Gel Pen series: Uni Style Fit Single Knock Gel Pen - Refillable - 0.28 mm and Uni Style Fit Single Knock Gel Pen - Refillable - 0.38 mm . These refills come with a nice colored case, which can be used as refill's storage case.
The UMR-109 gel ink features vivid colors and water-resistant ink formula.