The SMOK TF-STC2 are patented stainless steel dual coil heads with temperature sensing wire. The separate chamber design, provides drastic improvements for airflow, heat insulation and maintain full-flavored vapes. The TF-STC 2 by SMOK are compatible for both the TFV4 Tank and TFV4 Mini Tank. We highly recommend pairing it with the SMOK X Cube 2 or the Koopor Plus 200W TC Box Mod. The advanced replacement atomizer heads are constructed of high-quality stainless steel, with Clapton heating wire and 100% organic cotton. The SMOK TF-STC 2 Replacement Coil have a minimum resistance of 0.25 ohm and temperature range of 350 - 550 degrees Fahrenheit.