1321557C2 Lower Tube Trough Fits Case IH 1660 1680 1688 2144 2166 2188 ++ CombinOne New Aftermarket Replacement Lower Tube Trough Fits Case IH Axial Flow Combines This aftermarket replacement lower tube trough (grain tank loading auger lower tube) Fits Case IH (Fits Case International Harvester) Axial Flow combines. The lower tube trough is part of the grain tank loading auger system, channeling harvested grain from the clean grain elevator into the grain tank. It is the lower section of the two piece trough assembly and works in