This overpass works with HotWheels Track Builder tracks. The tracks easily slide on and are held firm. We printed this using 50% infill so it is strong enough for a child to play with without easily getting damaged. In the pictures you can see we printed this with three different filament colors to give it an interesting look. We used PLA plastic for this print. Build Time: 15 hrs 24 min Infill: 50% Plastic Weight: 0.55lb (PLA)