These are replacement heads for the iClear 16 Dual Coil Clearomizer. These replacement heads are 2.1 ohm.
Individual coils at $2.50 each or get quantities of 5 for $10.00 (when buying packs of 5, they drop to $2.00 each).
To change the replacement heads:
Just unscrew the bottom from the iClear 16 and the replacement head unscrews from that base. Screw the new head onto the base and replace the base onto the iClear 16.