This Fluency Activity is a part of the Lesson 4, Unit 3, Grade 2. These are often called base ten blocks. Dienes blocks include hundreds flats, tens rods, and ones cubes. They have not been formally introduced in Grade 2, and many students find them difficult to use at first. It may be appropriate to briefly identify each type of block before starting the game. However, avoid taking time to teach to the manipulative.