This monster mashup… well… stack-up, will bring some much-needed giggles to study time. OOLY’s Monster Stacking Highlighters feature 6 different highlighter colors: green, blue, purple, pink, orange, and yellow. And on each mini highlighter is a magnificent monster, ready to scare away those study nerves. For Ages 3 and up. WARNING: CHOKING HAZARD - Small Parts. Not for children under 3yrs.