Symptomatic Schatzki rings may be treated with esophageal dilatation, using bougie or balloon dilators. Vaginal dilators are required postoperatively to prevent vaginal stenosis from scarring. Tracheostomy uses skin puncture and dilators to insert the tracheostomy tube. The cervix may be dilated further using rigid cervical dilators which serially increase in diameter. Hegar dilators are used to treat vaginismus, also known as genito-pelvic pain disorder. Cervical canal widening can be temporarily achieved by the insertion of dilators into the cervix. Mild cases may be treated with local application of corticosteroids and pupillary dilators. Hegar dilators are widely used in gynecology to open up the cervix. If osmotic dilators were placed prior to the procedure, these are removed. Synthetic osmotic dilators are commonly referred to by their brand names, such as Dilapan. The dilators can also be used to sound the uterus. Over the guide wire the dilators are passed and a working sheath is introduced. More dilators are generally used with advancing gestational age. Hegar dilators are marked with a Hegar number equivalent to 0.5 millimeters. This can be done with Hegar dilators or similar dilators.