This is a refill cartridge for the Automatic Lip Pencil Duo. Snaps easily into place so you can change shades in an instant. Custom Lip Tool. The snap-in, snap-out cartridges let you create your own custom lip tool. For example, if you have an Automatic Lip Pencil Duo in one shade, try a refill in a second shade. Just snap out the lip brush cartridge and snap in the second shade for an ultra-convenient and very versatile tool.