The Vapefly Optima Coil is designed for Vapefly Optima Kit. The Vapefly Optima FreeCore Coil is a meshed coil with optional 0.3ohm and 0.8ohm resistance, The RMC Coil (rebuildable mesh coil) is perfectly for DIY fans. The RMC Coil is a cost-saving spare part. Just replace the mesh so the users will re-use the coil for about 10 times. Please select a suitable cartridge (Normal Cartridge & RMC Cartridge) to install the respective coils.