Smok TFT-4 is quadruple clapton core,resistance is 0.2ohm,work on 60w to 150w only $22 per pack with free shipping http://www.smokstore.us/smok/Smok-TF-T4 Smok TF-T8 is octuple fused clapton core,resistance is 0.16ohm,work on 60w to 180w only $24.15 per pack on smokstore.us with free shipping http://www.smokstore.us/smok/Smok-TF-T8