Sonifresh via Amazon offers its Sonifresh Replacement Toothbrush Heads 4-Pack for $10.99. (Select the "one-time purchase" option.) Coupon code "UJ3XDTV4" cuts it to $4.95. Plus, Prime members receive free shipping. (Non-members can order via Subscribe & Save for free shipping.) That's tied with our October mention for a similar 4-pack, $6 off, and the lowest price we could find. They're compatible with a range of toothbrushes including Philips Sonicare FlexCare, EasyClean, HealthyWhite, and Diamond Clean. Deal ends December 9.