Four heat settings and USB-C charging in a slim 510-thread battery. The Fernway Stylus is designed for Fernway cartridges, and it puts every control on a single button. Click three times to cycle through green (2.6V, most flavor), blue (3.0V), purple (3.4V) and red (3.8V, most vapor). Two clicks preheats for cold days or clogs. Four clicks checks the battery, and five clicks wakes it or puts it to sleep. Passthrough charging lets you keep using it while it charges. The lower settings bring out the most flavor.