Lash extensions have lately become a popular beauty accessory for many women. They come in three main types, mink, synthetic and silk. They measure from 6 to 17 mm. A special semi-permanent glue that does not irritate the eyes is used to stick them to the eyelids. The process could last up to two hours while the client could make visits every four weeks for light touch-ups that keep them in top shape till a replacement.