A thermoforming device is described. It relates to a mold assembly including a first and second mold, and to a mold that can be used in a thermoforming device. It also relates to a method for thermoforming a product. The thermoforming device is characterized in that the thermoforming device comprises a second pre-stretcher, in addition to a first pre-stretcher and a calibration element, and that the second pre-stretcher is at least partially and moveably arranged in a second mold body. A movement relative to the second mold body and towards the same forming cavity of the first pre-stretcher, the second pre-stretcher, and the calibration element, can be individually controlled, and the second pre-stretcher at least partially surrounds the first pre-stretcher and the calibration element.