This is the optional Heavy Duty Connecting Rod from Davis Model Products for the Traxxas 2.5 and 3.3 Engines. FEATURES: Stabilizes idle and overall performance and promotes longer piston and cylinder life Constructed of 2024 T4 aircraft alloy with two 660 bronze bearings at each end Oil holes located at each end to aid in lubrication of bearing surfaces INCLUDES: Heavy Duty Connecting Rod for the Traxxas 2.5 and 3.3 Engines REQUIRES: Partial disassembly of engine jxs 8/15/08 ir/jxs