Amazon offers the Crest 3D White Professional Effects Whitestrips Luxe 20-Treatment Kit for $34.99. Clip the $7 off coupon on the product page to cut it to $27.99. Plus, Prime members receive free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, it adds $5.48.) That's $3 under our March mention, which included two extra 1-hour express treatments, and the lowest total price we've seen. (It's a current low by $10.) This kit includes 40 Professional Effects strips (20 treatments).