  We report on the scattering parameters and Johnson noise emission of low-pass
stripline filters employing a magnetically loaded silicone dielectric down to
25 mK. The transmission characteristic of a device with $f_{-3dB}$=1.3 GHz
remains essentially unchanged upon cooling. Another device with $f_{-3dB}$=0.4
GHz, measured in its stopband, exhibits a steady state noise power emission
consistent with a temperature difference of a few mK relative to a
well-anchored cryogenic microwave attenuator at temperatures down to 25 mK,
thus presenting a matched thermal load.
