Features: Multi function math roller stamps support addition, subtraction, multiplication, and division practice to develop essential calculation abilities for children's daily learning. Adjustable rolling mechanism creates numerous random math problems to keep children engaged while enhancing computation speed and accuracy. Refillable design with included liquid bottle enables long term use for classroom or home practice with clear, consistent number impressions. Educational toy builds fundamental math skills, hand eye coordination, and focus for students through interactive activities. Compact size fits easily in school bags for convenient math practice during lessons, homework time, or educational trips. Specifications: Component: polylactic acid Size:Approx.7.3x7.3x6.5 cm/2.87x2.87x2.56in Color: 2 Option Package Includes: 1pc 4-in-1 Math Practice Roller Stamp note: 1.Please allow 1-2cm errors due to manual measurement, note that you donot mind before you order. 2.Due to the differences between different monitors, the picture may not reflect the actual color of the item.