1.Wide Compatibility Across Series: Our toothbrush heads are perfectly compatible with Waterpik Sonic Fusion series, including SF-01, SF-02, SF-03, and SF-04 models, providing a comprehensive replacement solution for your toothbrush. Check your model number on the bottom of your toothbrush base before purchasing. 2.US DuPont bristles: Our brush heads are made with DuPont bristles, the most representative of high quality nylon bristles. DuPont bristles have the following main advantages: high toughness, strong bending recovery, outstanding abrasion resistance and perfect cleaning power. The bristles are particularly gentle and comfortable for teeth and gums 3.Effective Cleaning: The electric toothbrush head's contoured top bristles naturally conform to the shape of your teeth, while the slim, angled neck and dense bristles reach hard-to-clean areas. The combination of dense bristles and powerful vibrations of the toothbrush head cleans up to 8 times more effectively than a manual toothbrush. 4.Indicator Bristle Tip: We recommend replacing the brush head once in three months. The brush head will become less effective after 3 months of use, but we'll remind you before that happens. The color of the indicator brush head will fade, reminding you that it's time to replace your toothbrush head to ensure your most effective cleaning.