Amazon offers the Optimum Nutrition Gold Standard 100% Casein Protein Powder 4-lb. Jar in Chocolate Supreme for $37.12 with free shipping via the directions below. That's the lowest total price we could find by $15, although we saw the same quantity of a different flavor for $7 less last week. To get this deal:

1. View the Optimum Nutrition Gold Standard 100% Casein Protein Powder 4-lb. Jar for $49.49
2. clip the 20% off coupon on the product page
3. add it to your cart via Subscribe & Save for a final checkout price of $37.12