The invention relates to a rotational unit (10) for a rotor of a dual centrifuge, said rotational unit having a bearing (14) and a rotational head (24) which is connected to the bearing (14), is mounted therein such that it can rotate about an axis of rotation and can be driven relative to the rotor by an additional rotational mechanism of the centrifuge, the rotational head (24) being detachably connected to the receiving unit (40, 80) for conjoint rotation, which receiving unit comprises a sample container receptacle (60, 70, 100, 110) for at least one sample container. The invention is characterized in that the receiving unit (40, 80) and the rotational head (24) are connected by a frictional connection in which some portions of the receiving unit (40, 80) and the rotational head (24) engage in each other in a wedge-like manner, and the frictional connection increases with a movement of the receiving unit (40, 80) along the axis of rotation of the rotational unit (10) in the direction toward the rotational head (24).