The mouthpiece assembly is a replacement device for your Boundless CF and Boundless CFX. When you purchase the set, you should expect the full mouthpiece, along with the seal, cooling unit, stainless screen and the O-ring. This is an original factory replacement so you can be assured of a perfect fit for your vaping device. You don’t need any modifications when you buy the Boundless mouthpiece assembly set. You need to replace the mouthpiece every now and then to ensure that the vaping experience is not diluted by the stale taste or the airflow is restricted due to the filters and mouthpiece.