Kirakira Secret Pen Pink, New, Unopened ◆ Letters appear when exposed to a black light! First, write letters or draw pictures with the pen. At that time, the letters and pictures are invisible. Next, when you shine the black light on the cap, the written letters and pictures will appear, which is fun! Uses 3 LR1130 button batteries (test batteries included) Body size (approx.): 134 x 16 x 17mm