Walmart offers the Crest 3D White No Slip Whitestrips Professional Effects 40-Treatment Pack for $44.88 with free shipping. That's the best deal for this quantity today by $14, and at $1.12 per treatment, it's tied with the lowest per-treatment price we've seen. (For further comparison, we saw a 20-treatment pack bundled with two express kits for $29 three weeks ago.) These strips purportedly remove up to 14 years' worth of stains.