No one has yet produced such an innovative replaceable coil for an RTA tank until now, except of course, Aspire. The fantastic all new coil design, the ARC, 'Aspire Radial Coil' which sits horizontally in the tank similar to a 'stove-top' design. Of course the real trick in the design is the increased surface area of the coil for great flavor and great vapor production, made using Kanthal material and rated at 0.10-0.16ohm.