Product DescriptionSmart Math Roller Stamps compatible Math Problems: one addition stamp, one subtraction stamp, 2 bottles of inkInteresting School Supplies:The math stamp set as fun as toys, makes learning fun and exciting, increase children's interest in learning compatibleable compatible students to practice, parent guidance, teacher teachingSave Time: Easy to operate the math questions can appear in front of you by scrolling the stamp, which can be adjusted, and the questions can be changed by gently twisting the button, and the questions will be randomly selected.Refill Pack: DurableEquipped with 2 Free refills ink, open the oil cap and drop 5-6 drops at oncePackage include:2pcs/Set x Roller StampsNote:1. Due to the different monitor and lighting effect, the actual color of the item may be slightly different from the color shown on the pictures.2. Please allow 1-3cm error due to manual measurement. (1 inch = 2.54 cm)Thanks compatible your support :)