The size of the toothbrush head: the length of the toothbrush head should be 2.5 to 3 cm, the width is 0.8 to 1 cm, there are 2 to 4 rows of bristles, each row of 5 to 12 bundles of bristles, the front end of the toothbrush head should be round and blunt. These rules can be used for reference when people choose toothbrushes. https://www.samemater.com/toothb...-children-s-plastic.html