You must follow these steps to get the deal
1. Log into you Amazon Account
2. Click Here
3. Scroll Down to where the coupons are ("your coupon book")
4. Refresh the page repeatedly until you see "Save $7 On any ONE Advanced Vivid 14ct, Professional Effects, Gentle Routine, Stain Shield, Premium, Advanced Seal 14ct, Pro Effects, Daily Whitening Multicare, Daily Whitening + Tartar (excluding Classic)"
5. Click the coupon link & add either Crest Whitestrips Pro Effects,10-Day Dental Whitening Formula System, 40 Strips or Crest Premium White Strips, 28 Count to cart
6. From the cart click on the product link
7. Once at the product page choose Subscribe & Save and proceed through checkout.
8. Your total for either item should be as listed below. (+ tax if applicable)

Crest Whitestrips Pro Effects,10-Day Dental Whitening Formula System, 40 Strips
Items: $23.26
Shipping & Handling: $0.00
Subscription Discount: -$3.49
Your Coupon Savings: -$7.00
Order Total: $12.77
Crest Premium White Strips, 28 Count
Items: $22.82
Shipping & Handling: $0.00
Subscription Discount: -$3.42
Your Coupon Savings: -$7.00
Order Total: $12.40
You can always cancel S&S anytime after placing your order. There also is a limit of one coupon use per account.
Thanks CricketShops