Like hair extensions, eyelash extensions add length to human eyelashes eyelash. Synthetic single fiber polyester thread-like materials are applied to eyelashes to create a fuller, longer look. Extensions come in various lengths, colors and thicknesses, and can be worn during sleep, showering and swimming. However, excessive exposure to oil can weaken adhesive bond.Silk Eyelashes are a great way to have beautiful eyes without the need for mascara.