ISO 8009-8:1985

Reusable rubber contraceptive diaphragms — Part 8: Determination of twisting during compression of coil spring and flat spring diaphragms

Specifies a measuring method. This method is not applicable to diaphragms with springs designed to form an arc when compressed. Compression of the rim of the article across its diameter using a suitable apparatus. Determination of the deviation of the rim from the horizontal plane.