Hegar Uterine Dilator, Sklar, Double End 3mm/4mm, Curved, Stainless Steel. Sklar's Hegar Double-Ended Uterine Dilator is a manual, probe-style instrument used to dilate the cervix. They are solid, nonflexible, and available in multiple diameters. These dilators are slightly curved in opposite directions from the center and have smooth, rounded tips. This product is the 3mm/4mm dilator. The overall length is 8 inches.