What is Caya®? Caya® is a single size silicone diaphragm with an oval contoured shape, and a flexible rim. The manufacturer recommends using a lactic-acid-containing gel as a lubricant. The gel is applied to the diaphragm, the rim is squeezed and the diaphragm is inserted into the vagina. It sits across the vagina and covers the cervix. One end of the rim sits high up behind the cervix and the other tucks under the pubic bone in front.