I'm not sure why exactly, maybe because silver is a conductor, possibly it is the gel adhesive, but these silver lined are the pads I prefer most!
With my old tens unit after having sampled many different pads, it was the silver lined I found worked best for me.
This gel adhesive also seems to be the one I have no reaction to, and they reapply well for several uses.
They do cost a little more, for me well worth it.
