Complete set of scattering parameter measurements in the linear (S-parameters) of active and passive DC and RF components within the millikelvin temperature range and under probes composed of a few photon excitations. This includes the extrapolation of device-specific figures of merit, such as matching, input, and return losses, with respect to a cryogenic reference. RF measurements within the 4-12 GHz bandwidth and 20-900 mK temperature range. DC biasing lines are available. The devices should be connectorized (3.5 mm / SMA). Specific parameters for excitations, as well as necessary filtering and shielding requirements, will be discussed with the customer. In consultation, measurements requiring additional RF ports and pulsed microwave drives could be performed.