Amazon offers the Crest 3D White Luxe Whitestrips Professional Effects 20-Treament Pack for $36.76. Clip the $7 off coupon on the product page to drop it to $29.76. Plus, Amazon Prime members bag free shipping. (Non-members can spend $49 to qualify for free shipping; otherwise, it adds $5.48.) That's about $7 under what you'd expect to pay in local stores. These strips purport to remove up to 14 years of stains.