Abstract: A tank trailer to transport flowable material may include a frame. a tank to hold the flowable material connected to the frame, and the tank may include a first section, a second section connected to the first section and a third section connected to the second section. The first section may include a first diameter and the third section may include a second diameter. The second section may include a decreasing diameter to connect the first section and to connect the third section. The decreasing diameter may include a inclined surface, and the second portion may include an inclined side surface. The second portion may include an inclined bottom surface, and the tank trailer may include a convex front wall. The tank trailer may include a convex back wall, and the tank trailer may include a rib. The tank trailer may include a king pin.