A tank trailer configured to lower an overall center of gravity. The trailer includes a tank, a wheel assembly, an upper body height and a trailer length. The tank includes a cavity contained within a lower body, an upper body, a transitioning body, a front end and a rear end when the cavity within the trailer is filled with a liquid fluid, the liquid fluid is evenly distributed along the trailer length of the trailer since a diameter of the lower body, the upper body and the transitioning body are equal. Other trailers are presented.