The Captive Cap by Dynavap is the same as the standard cap apart from one big feature. And that is the little indents on the side of the cap which holds it on the tip. In all other dynavap cap versions the cap has to be bent into an oval shape to get it to stay on especially in use. The Captive Cap requires only a very light oval shape to stay on which gives more even airflow in between the tip and cap.
The cap is made out of medical grade stainless steel and is engineered to click 1-2 times once it reaches the correct temperature. Please keep in mind the overall temperature will vary tempeding on your heating technique.
The cap is also designed to be a very handy tool. With its main job being scooping out spent herb. But is also handy for other tasks as well. Pretty sure Macgyver played a part in the design of this handy little cap.