MPS Microsystems manufactures the dosing unit of an implantable variable flow peristaltic pump. This programmable pump delivers pain medication into the patient's intrathecal space. The dosing system has three arms, each consisting of a ball bearing, in order to limit friction as much as possible when the peristaltic pump is in operation. The dosing accuracy is achieved by a spring that applies the force necessary to occlude the flexible tube connected to the catheter. The repeatability of this force is guaranteed thanks to a meticulous assembly of the components in an ISO 7 clean room and the total absence of particles. The torque, spring stiffness and geometry of the assembly are 100% controlled.