Philips Sonicare E-Series replacement toothbrush heads, HX7023/30, 3-pack - $21.95 after coupon or less with S&S on Amazon
Great deal on Sonicare E Series brush heads (original phillips brand). Clip the coupon on the right for 5 dollars off. Use subscribe and save to save a bit more. This is cheaper than anywhere else I've seen in a while per brushhead.