Feature: 1. Engraved Symbols: The symbols on the surface of the dices are engraved, so the minus and plus symbols on the dices will not be worn even after long term use. 2. Plastic Material: These math operation dices are made of premium plastic material, which is not easy to be damaged and can be used for a long time. 3. Development of Intelligence: These math calculation dices are applicable to infant education and has a helping role in developing children's intelligence. 4. Attention Attracting: The math dice set adopts dice shape design, which can well attract children's attention and let them participate in mathematical operations. 5. A Perfect Toy: This plus minus dice set can be used as a perfect toy for children. While entertaining, children can also learn some mathematical knowledge. Specification: Item Type: Plus minus dice set Material: Plastic Weight: Approx. 80g/2.8oz Product Size: 1.6x1.6x1.6cm/0.6x0.6x0.6in Applicable: Mathematics teaching. Package List: 20 x Dice Note: 1. Please allow 1‑3mm error for manual measurement, thank you!2. Due to the difference between different monitors, the pictures may not reflect the actual color of the items.3. Children should use the dices under the care of their parents.