Juliemay
Juliemay is one of the few natural-fiber brands that seriously addresses larger busts and underwire, a gap most plastic-free lingerie leaves open. Bras pair GOTS organic Pima cotton with a pure-silk lining and are marketed as free of harsh dyes, synthetics, exposed elastics, and nickel. The material honesty caveat is that a supportive underwired bra still needs some stretch and structure; the brand emphasizes natural fibers and covered/non-metallic components but doesn't publish a full elastic breakdown, so a small covered synthetic stretch element can't be ruled out.
How clear are their specs?
Publishes the main fabric composition (e.g. 78% organic Pima cotton / 22% silk, 100% silk lining) and notes non-metallic underwire and fastenings, but does not fully specify the elastic/stretch fiber.