Device for the simultaneous fixation of medical instruments, the device having a joint member which has a holding section in the form of a spherical segment, the spherical segment having a continuous cavity along a longitudinal axis, the holding section being subdivided into at least two holding segments perpendicular to the longitudinal axis, and at least two arm elements being arranged on the joint member, the apparatus further comprising a tension ring supported by the support surfaces and a tensioning element configured to press the support segments together, wherein when the support segments are pressed together, the support surfaces press against the tension ring. Furthermore, a system with such a device is revealed.