Alpha Gold Aluminum, race geometry, internal front derailleur routing, Solo Air spring, TurnKey lockout. X-Caliber will get you hooked. It packs all of Trek’s XC race hardtail experience into a light, fast, race-ready bike that pairs the right wheel size with each frame size. Nothing beats the efficiency, simplicity, and straight-up fun of an X-Cal hardtail in 29er or 27.5". Great for XC racing, marathons, 24-hour racing, or simply shredding singletrack.