Part 2: Polystyrene capacitor
Polystyrene capacitors provide high insulation, low leakage, low dielectric absorption, low distortion and excellent temperature stability.more details can be find at:
https://www.electronics-notes.com/articles/electronic_components/capacitors/polystyrene.php
Polystyrene capacitors are not widely available these days ,and only as leaded components. A typical application will be diy marx generator. See-
https://yanlania.com/products/marx-generator-6-stage?_pos=1&_sid=2d9008721&_ss=r