Alan R., Thanx for citing that study. Clearly I missed it when I did my research. I note that it was a 2011 study and did not evaluate the improved models. The later anecdotal reviews are good. I guess I need to do more research and be prepared to replace my TK 4Ls , if I cannot find substantial improvement over the loner term. Mine worked fine, i.e. held and rendered lower pulse undetectable, when I tried the on myself. But you got my attention big time!