Also known as "Vivi Cone" This sleeve is to make a more natural transition between the atomizer and the battery. Will work for any atomizer that has a flat bottom with the threads protruding from the bottom plate. (Don't worry, if yours protrudes, you know it) Primarily the Vivi Nova and the Mini Vivi nova as well as the Protank and DCT'S. Comes in large and small. Small works great with the DCT'S and the Mini Vivi!!