I have the 6L (6 lead) but use the single lead function more often. In fact I use it most of the time.

The 6 lead EKG is done on the skin of your knee, with two fingers on each side of the device. The single lead is done with two fingers on either side of the device, on any flat surface (away from electromagnetic interference). Results go on your phone.

When I am in a troublesome period (when I had COVID, or after an episode) I also pay for "advance determinations.," which shows PVC's and other abnormalities. This works with the single lead.

I got mine several years ago but it looks like Kardia has the one and six models still ($79 and $129) and a new card type for $99. I change the battery every so often at a jewelers.