Stove Mica or Isinglass
Stove Mica is used for replacement in older Wood stoves. It is available in Spotted and Clear, Part number are specified with a C or a S at the end of the size for that color.
Remove retaining plate to determine size & quantity required. Several small pieces of mica are much lower priced than 1 large piece.
The thickness of mica varies from 0.003" to 0.005".