BAK Industries manufactures some of the most secure and versatile tonneau covers on the market today. Two particular BAK covers, the MX4 and Revolver X4, have proven to be popular with thousands of truck owners. While they have similar-sounding names, these two covers have little in common besides the letter X and the number 4. In this article, we explain the differences between the MX4 and Revolver X4 so you can choose the best cover for your truck.