Abstract: A filter for preventing the infiltration of contaminants into a kinescope envelope, includes a ring having a sloped surface to conform with the conical section of the kinescope neck. The ring also includes a support portion to which is affixed a non-oxidizable fluid permeative member. The ring is configured and dimensioned to rest against the inside surface of the conical neck section through a temperature range of approximately 20.degree. C. to 500.degree. C. so that fluid enters the envelope only through the permeative member. Specially configured clips remain resilient throughout the 20.degree. C. to 500.degree. C. temperature range to hold the filter in the conical section.