They were quite common in the day of 12 or 15 watt regulated tube mods like the old Evic or the Smoktech SID that had a maximum amp draw of 4 amps and chip protection. They were the factory cell in the Evics at the time. Being ICR chemistry they are completely unsuitable for use in a mech and of no use whatsoever in current production mods as it simply doesn't have the amps (5.2A) and suitable safe chemistry batteries (IMR, INR) are widely available with much higher amps for the same or even a lower price today.