The main difference between the Z-Trek and Z-Trail is the sole. The Z-Trek has a 5.5 mm solid rubber sole that is extremely flexible and allows the most ground feel. The Z-Trail sole has a 11 mm sole made up of 3 materials: rubber and Trail Foam for the outsole, and a soft layer of BareFoam for the top sole. While still light and flexible, the Z-Trail sole does not offer as much ground feel.