Weirdly, the hats remind me of things used for the opposite purpose -- diaphragm birth control (c.f. https://healthjade.com/wp-content/uploads/2018/06/coil-spri

Weirdly, the hats remind me of things used for the opposite purpose -- diaphragm birth control (c.f. https://healthjade.com/wp-content/uploads/2018/06/coil-spring-diaphragm.jpg https://healthjade.com/wp-content/uploads/2018/06/coil-sprin...), or rolled condoms.