This is an optional HPI Heavy Duty Differential Shaft for Nitro RS4 3. This part replaces the stock diff shaft. FEATURES: Heavy duty steel construction Lightly polished YOU WILL RECEIVE: Two HD diff shafts REQUIREMENTS: Installation onto HPI Nitro RS4 3. SPECIFICATIONS: Total length: 21mm (0.83") cmc 03/03/05 ir/jxs &