If you require close tolerance [1% is standard] capacitance [from 4 to 100,000pF and greater] that stays rock steady for the life of your equipment, that is little affected by temperature changes or radiation, and that combines high Q with high insulation  resistance then silvered micas from TAB Components Ltd. are the ideal answer.
They are intended for applications in professional and military equipment where high quality and precision are paramount, such as oscillators, logic and transmission circuits and pulse forming networks.

TAB manufacture sintered silvered mica capacitors made from the best quality mica and  produce a standard resin moulded
radial product range, a standard radial resin dipped range and also two ranges of high frequency, high voltage capacitors with
operating frequencies up to 30 MHZ .
ALL TAB MICA CAPACITORS ARE RoHS COMPLIANT.
[ EXCLUDING HIGH TEMPERATURE TYPES THAT HAVE
LEADED SOLDER IN THEIR CONSTRUCTION].
TAB mica capacitors perform extremely well in high
quality audio equipment giving excellent sonic qualities
because of their unique manufacture and use of non magnetic materials in their construction.

COMPANY PROFILE.
The company holds BS.EN.ISO  9001:2008 international
standard and was founded in 1986 employing staff who
originally worked in the mica capacitor industry, TAB exports worldwide and supplies many major electronic equipment manufacturers.