Sonifresh via Amazon offers its Sonifresh Replacement Toothbrush Heads for Philips Sonicare 8-Pack for $16.99. Coupon code "ICUTA68O" cuts it to $7.65. Plus, Prime members receive free shipping. That's $9 off list, and the lowest price we could find, although we saw them for a few cents less in our May mention. They are compatible with various Philips Sonicare handles.