The Uwell Crown 4 SS904 Replacement Coils come with a threadless plug and play design and high quality superior Stainless Steel heating elements for a smooth vape. As pre-installed in the Uwell Crown 4 Sub-Ohm Tank, is the SS904L 0.4 ohm Dual Coil rated for use between 60-70W. Rated for similar mid-wattages is the SS904L 0.2 ohm Dual Coil recommended for best use between 70-80W. The unique Stainless Steel heating element of these coils is commonly used in luxury wristwatches and provides corrosion resistance. Alongside the Stainless Steel within these coil heads, you will find 100% Organic Cotton Fiber for optimal wicking with your favorite e-liquids. On the Stainless Steel frame of these atomizer heads are three long vertical wicking ports that will keep your e-juice flowing to the coil from the Crown 4’s massive 6mL glass reservoir. For these coils, Uwell has utilized Pro-FOCS flavor tasting technology to ensure you get a truly satisfying vape with a balance of flavor enhancement and cloud production.