Abstract: A retractable assembly, comprising: an assembly housing; a linear drive in the assembly housing; and a tubular holder), movably guided between a measuring position and a service position by means of the linear drive, for fluid-sealed reception of a sensor, with which a physical and/or chemical process variable is determinable. The linear drive includes a piston seated movably in a cylinder and loadable with a pressure-bearing medium on one or both ends and the tubular holder is fixed in the piston. The piston has on its working end active for the measuring position a breach in the direction of the interior of the tubular holder.