Mixing the perfect balance of speed and stability, the GEL-DS Trainer® 21 shoe continues to incorporate all the treasured features with a touch of newness. Lightweight Dynamic DuoMax® Support System and Propulsion Trusstic® Technology provide a stable ride while the new Seamless Upper creates a better and more comfortable fit. Linking all the componentry together is the I.G.S® (Impact Guidance System) Technology which improves the foot’s natural gait from heel strike to toe-off. Weight: 7.7. Heel Height: 19.5mm. Forefoot Height: 9.5mm.