The Yuuki cup is made out of medical grade silicone. It is made out of a clear, translucent silicone and has ridges on the outside of the cup as well as on the stem.
They offer two sizes of cup, a small cup and a large cup. Which one is right for you depends on whether you've given birth to a child, your age, and your flow. If in doubt, they recommend buying the larger cup since you can save it for later.
In addition they offer two levels of firmness, classic and soft. Soft may be more comfortable for some women but may also be more prone to shifting with movement and leaks. On the other hand, classic is firmer and should leak less.