FriXion Ball Knock Zone. This new version of FriXion pen comes with a few new upgrades and a new version of FriXion refill that writes darker and longer. As opposed to the the regular FriXion refill, the new FriXion Zone refill comes in metal encasing with “Premium FriXion Ink”, which writes 30% higher density in black, and 15% higher density in black and blue. The new metal encasing is thinner, allowing the ink capacity to increase by 70%. Two pen upgrades include a more fitted grip section to reduce rattling of the refill, as well as an additional spring to soften the impact of knocking. FriXion Zone comes in muted tones as well as more professional grip such as birch wood and marble resin.