It depends on the tonneau cover and how much depth you have in your bed from the bottom to the bed rails. The Travel Trekker won't fit with a retractable tonneau cover that uses a canister. You should be able to clear most roll-up tonneau covers (like the TruXedo TruXport, Deuce, Lo Pro, etc.) that have slightly raised rails. You may have issues with any low-profile folding tonneau, especially those that have fairly thick panels. This part number is actually semi-universal and should fit and function on a 2020 GM 3500 Duramax.