Men's Nike Train Speed 4 Training Shoe. LIGHTWEIGHT DURABILITY. LOCKED-DOWN FIT. Men's Nike Train Speed 4 Training Shoe features a synthetic upper and Flywire technology in a chain link pattern for lateral movement support. Designed for everyday workouts, it features aggressive traction that enhances grip on all surfaces. Synthetic upper provides lightweight durability. Flywire technology provides a locked-down fit. Aggressive traction pattern on the outsole enhances grip. Inner sleeve construction made of lightweight, breathable mesh provides a sock-like fit. Injected unit (IU) sole is tough enough to double as an outsole, dramatically reducing the overall weight.