Traxxas 4400 Nitro Engine Upgrade Kit from .15 to 2.5 Kit makes it easy to upgrade your .15 nitro-powered vehicle to the awesome power of the 2.5R racing engine Includes header, pipe, pipe hanger, coupler, linkage, and additional components specific to each model Major components come pre-assembled and pre-adjusted from the factory Detailed instructions are included Use Traxxas stock and hop-up replacement parts to get the most out of your Traxxas RTR vehicles