Fluorescent Writing Pen 1. Have CE certification 2.15mm core size,six colors. 3. 5mm or 8mm core size,this can change freely. Fluorescent Writing Pen1 Fluorescent Writing Pen have CE certification.2 15mm core size,six colors.3 5mm or 8mm core size,this can change freely,6 colors.4 It must be used together with fluorescent writing board. Fluorescent Writing Pen