This is an optional Serpent gear differential set for the Serpent SRX 2. This gear differential features a compact composite housing and a 51T gear. The specially designed shape delivers super smooth differential action, while silicone seals provide a leak proof assembly. One of the housing sides has four small metal threaded shaped nuts, which key into slots and sit flush with the case, and four screws insert from the other side and tie the two halves together. The outdrives are Serpent Spring Steel and are machined on both sides to reduce weight. The full assembly weighs only 28.9 grams without oil and can be installed with no modification. Serpent recommends 7000cst oil as a starting point.