Fun Express: These classroom supplies are a fun way to measure game period, recess, debates and other timed events! Simply wind these timers all the way up, then set your desired time. Each timer goes up to 1 hour. Great gifts for teachers, these plastic timers are useful at day cares, preschools and school field days! Use them for exams and reading period to keep your school day on schedule. Plastic. (3 pcs. per unit) 3" x 2 1/2" diam.