We all want to be in the beauty know, so here is the lowdown on lash extensions! There are different curls, thickness and length of extensions. Thickness varies from .03-.3 mm, and lengths range from 4-20 mm. Lashes are applied one at a time using a specially formulated semi-permanent glue made to not irritate the eyes or damage your natural lash. There are different types of glue made specifically for those with sensitivity. In addition, you will find different types of sets, depending on what the lash artist is trained in, including classic and volume. With classic sets, one extension is attached per lash. With volume sets, 2-3 lash extensions are attached to each lash.