The Saucony Xodus Ultra is an upgraded version of the original Xodus trail running shoe, designed for serious trail runners. The shoe features a thicker midsole made of PWRRUN+ foam, providing greater cushioning and energy return than the original. The outsole is made of PWRTRAC rubber, which provides better traction on rugged terrain, and the upper is made of a more breathable FORMFIT material. The shoe also includes a gaiter attachment point and a lace garage to help keep debris out. Overall, the Saucony Xodus Ultra offers superior cushioning, traction, and protection, making it an excellent choice for serious trail runners.