Caya is a contoured diaphragm that was approved by the FDA in 2014. In addition to being shaped differently than Milex, it is made of stronger but thinner material and is more flexible for a better fit. It's one size fits all, meaning there's no need for fittings – just a prescription. Some health care providers may have free "test fit units" to help you decide if Caya is right for you.
Milex is the standard diaphragm prescribed by doctors in the US. Like its predecessor, Ortho All-Flex, it's circular in shape and comes in 7 different sizes so you'll have to do a fitting by a trained health professional first.