Avoid Residue Build Up - It is recommended that you replace your brush head every 3 months to make sure your smile continues to improve, because residue builds up on your toothbrush head over time, which blocks our Blue Lightwave technology. Color Changing Bristles - The blue precision cleaning bristles on our replacement toothbrush heads change color to indicate when it’s time to replace the brush head. How To Change The Brush Heads - Gently squeeze the sides of the brush head currently on your compatible GO SMILE toothbrush. Pull head away from handle. Slide new head in place until bottom of brush head firmly meets the toothbrush. Brush head is the only replacement part needed. No expensive mechanical parts. This set of replacement brush heads fit the GS494W Smart Sonic On-The-Go Blue Light Technology Toothbrush. Created by a dentist, GO SMILE has been whitening smiles for nearly 20 years. Based in the San Francisco Bay Area, we have revolutionized at-home and on-the-go teeth whitening products that are safe, effective and clinically proven to whiten with no sensitivity. Our products are known for their innovation, ease of use and award-winning results.