Product Features:
"Premium Frixion Ink" has a 30% higher ink density for black and 15% higher red and blue than conventional "Frixion Ink (Frixion Ball single-color refill)", allowing for dark and highly visible writing. 
In addition, by using metal refills with thinner pipes, the ink capacity per refill increases by 70% compared to conventional resin refills, making the ink last longer.
It is compatible with conventional friction ball refills for single colors, so it can also be used for friction balls and friction ball knocks.

Product Specifications:
Size: Total length: 111.02mm Maximum diameter 6.1mm