There are some differences among the five IUDs. The biggest is that the copper IUD (Paragard) is non-hormonal, while the other four (Mirena, LILETTA, Kyleena, and Skyla) contain a hormone called levonorgestrel, which is a type of progestin. While they all work very well to prevent pregnancy, the non-hormonal IUD can have different benefits and side effects than the hormonal IUDs, and the four hormonal IUDs have some differences among them as well. Which IUD is best for you depends on what’s most important to you.