The Stem Cap Pack Pack for the Arizer Solo comes in a four-piece set. The product is also compatible to be used for the Arizer Solo 2, Arizer Air, and the Arizer Air 2. The plastic is fabricated out of superior-quality silicone. It’s insulated to ensure that it resists heat to a certain degree. The plastic caps are meant to protect your pocket or bag from the heated glass tubes. You can also use these to preload stem tubes so you can vape all day. If you only vaped halfway, you can use the caps to store away the rest of the contents to be used for later.