I would like to iterate through a folder of input rasters and at the same time iterate through a folder of target rasters to run the Mosaic tool. The folder contents are such that InRas1 should mosaic with TargetRas1 to create Mosaic1, and so on with rasters and targets 2, 3, 4, etc. The thumbnail images show my approach so far. The problem is the model iterates through all of the Input rasters , then all of the Target rasters, and only mosaics the last one from each. I have tried putting in preconditions in various places, but may not be using them correctly, since I don't fully understand them. Thanks fo any help.