Refills for FriXion Synergy Knock, Friction Point Knock, Friction Point Knock, and Friction Point.. Not for use with other products. Black, Red and Blue are only available in sets of 3. 【Ink Color】 Black 【Ball diameter】 0.5. Size: Height 5.3 inches (135 mm), Width 0.8 inches (20 mm), Thickness 0.3 inches (7 mm). Product Color Trend:Black