Mica Capacitors

These capacitors use Mica for the dielectric. Mica capacitors have good stability because their temperature coefficient is small. Because their frequency characteristic is excellent, they are used for resonance circuits, and high frequency filters. Also, they have good insulation, and so can be utilized in high voltage circuits. It was often used for vacuum tube style radio transmitters, etc.
Mica capacitors do not have high values of capacitance, and they can be relatively expensive.

Pictured at the right are "Dipped mica capacitors." These can handle up to 500 volts.
The capacitance from the left
Capacitance: 47pF (printed with 470J)
[the width 7mm, the height 5mm, the thickness 4mm]
Capacitance: 220pF (printed with 221J)
[the width 10mm, the height 6mm, the thickness 4mm]
Capacitance: 1000pF (printed with 102J)
[the width 14mm, the height 9mm, the thickness 4mm]

These capacitors have no polarity.