This multi pen features four of Pilot's smooth-writing Acroball inks in black, blue, red, and green. The oil-based ink has 1/5 of the viscosity of conventional oil-based inks. The unique blend of ink and lubricants allows the ball at the tip of the pen to rotate smoothly by reducing friction. This creates an enjoyable, non-skip writing experience. The ink is satisfyingly pigmented and is also water-resistant. The pen has a unique rubber grip developed by Pilot that sports a tire pattern, which prevents your hand from slipping. The clip on the pen uses a coil spring with a "soft clip" mechanism that can be clipped 100,000 times without breaking, according to Pilot's testing. Not only is it durable, the clip is extremely easy to open and use.