2 layer YY lashes are an easy and cost effective way to add light volume to your clients lashes since they are similar to 2D fans. Each lash has a split tip which creates the Y look. The bases are straight and provides a nice contact space for fantasic retention. The application is similar to a Classic lash. 
Many artists are choosing to use YY lashes as their hybrid sets. It's faster, easier, and a more cost effective method of providing light volume.