A menstrual cup is a menstrual hygiene device which is inserted into the vagina during menstruation. Its purpose is to collect menstrual fluid (blood from the uterine lining mixed with other fluids). Menstrual cups are usually made of flexible mediacal grade silicone, latex, or TPE. You can read more here. Most menstrual cup brands sell a smaller and a larger size. Your cervix hight will show which size is the perfect for you.
Good for your body: Menstrual cups are a safe option relative to other forms of menstrual hygiene.
Good for nature: Since they are reusable, menstrual cups help to reduce solid waste.