Today, Jan. 18 only, Amazon is offering up 60% off Optimum Nutrition products. This makes for some does deals on protein, pre-workout, and more! That makes for a nice deal on this highly rated 100% Casein Protein Chocolate 4 Lb. on sale for just $37.63 (reg. $82.45!). You’ll also snag a FREE sample of Cellucor C4 Pre Workout Supplement when you click the box located under the product price (look at the picture below for more details). Sweet!