Show How You Worked It out - 30mmThis 30mm self inking stamp is a must have for any teacher. It is the perfect size for marking papers, grading tests, and providing feedback to students. The stamp is also self inking, so you can save time and hassle by not having to refill it with ink. The stamp is available in a variety of ink colors, so you can choose one that matches your personality or classroom dcor. Features: 30mm round size Self inking Available in a variety of ink colors