Silicone is an elastomer (rubber-like material) that offers many benefits. Features of silicone include resistance to extreme temperatures, elasticity, and chemical stability. It's heat resistant, so it makes a great ashtray. It's highly flexible so it can create a water-tight seal like the Pulsar Plug. And silicone is both slip-resistant and non-binding, meaning it can be both sticky and slick. In other words, a silicone tray will keep a water pipe from sliding, yet a sticky dab won't stick to it.