Includes: 4 Silicone Stem Caps for pre-loading Glass Aroma Tubes, and / or protecting pockets, purses, and surfaces from hot glass. Made with high quality, food / medical grade, heat-rated silicone. Compatibility: Solo / Air II Glass Aroma Tubes, Solo / Air II Tipped Glass Aroma Tubes, Solo / Air II Frosted Glass Aroma Tubes