Bela Fleck came into the shop during the Telluride Bluegrass Festival one year. Most of his peers had already gotten hip to Blue Chip, so he was on the hunt for one of their thumb picks. At the time, we were sold out of the Blue Chip JD (a very popular thumb pick for banjo players), and all we had were Reso's. He bought one anyway. Fast forward a couple years to another Telluride Bluegrass Festival where he was doing a workshop at the Transfer Warehouse. Someone in the audience asked him about picks, and he responded with a story similar to the one above. However, he discovered the longer blade helped him with a more consistent "single-string" picking style, and has been picking with Blue Chip Reso's ever since.
Not that it matters after hearing the Bela Fleck endorsement, but this is also Warren's preferred banjo pick.
From Blue Chip:
"This is our dobro/resonator thumb pick in a size medium. This is a slightly thicker blade design as compared to our banjo picks to withstand the more strenuous use on a dobro. It is constructed using a custom designed stainless steel band and a 60/1000 of an inch(1.50mm) thick BlueChip pick. These picks are laser etched, professionally machined, and hand beveled to create the best thumb pick available."