Type IXC was a further refinement of the class with storage for an additional 43 tonnes of fuel, increasing the boat's range, in Nazi Germany's Kiegmarine Navy. This series omitted the control room periscope leaving the boats with two tower scopes.
As mine-layers they could carry 44 TMA or 66 TMB mines, though U-162 through U-170 and U-505 through U-550 (35 boats), were not fitted for mine operations. One IXC carries the distinction of being the only U-boat sunk in the Gulf of Mexico, U-166.
U-505 survives at the Museum of Science and Industry in Chicago, and as of 2005 has been completely renovated.