FriXion Point Knock is a hybrid pen of FriXion erasable ink with Juice-Up body/tip. A typical FriXion pen comes in either needle point or metal point. This new tip gives FriXion pen a different writing experience that feels just as fine as a needle point but as smooth as a metal point. FriXion Point Knock – 0.4mm More FriXion pen colors and options here Available in 8 Color Set Refills available About FriXion: The FriXion ink is erasable by rubbing with the tip of the pen to create the frictional heat needed for the ink to disappear. Since the ink reacts directly to temperature, it is recommended not to leave it under direct sunlight or anything that’s hotter than 140 Fahrenheit.