The brush head that came with the product is too small
Response from waterpik.comBy WaterPik, Product Support, January 10, 2023
Hello Michael - Thank you for your feedback. The toothbrush head is designed to be small to fit in the back of your mouth at the correct angle for flossing. This does not make brushing any less effective. We appreciate your comments and will pass along this information to our Product Design team.