Great trail shoes. Favorites of mine. Ready to upgrade! Have worn these for gym sessions to long trail runs. The Primus Trail II Firm Ground is our original, best-selling trail-running sneaker. It’s light, durable and flexible for wide-ranging trail adventures that bring you closer to the earth. Continuously improved through athlete testing and material innovation, the Primus Trail II FG has nothing more or less than exactly what you need – made with high-performance, recycled, vegan* materials.