CR's XP/ XR/ XM Tunnel Extension Kit is used to either extend your stock tunnel for a longer track, or repair your existing stock tunnel. All installation hardware is included (stainless steel button head bolts & nuts). Tunnel extension side plates are constructed of 3/16 6061 aluminum. Extensions caps are made from .065 6061 aluminum. Please select your size and finish below. Tunnel reinforcement plates can be ordered separately, call or e-mail for more details.