This FLEX version is based on the classic TORTEX formula but mixed with nylon to create a slightly more flexible feel and warmer tone.
TORTEX is the pick used by the top musicians worldwide, and has been for decades.  The Tortex material is made from a treated Delrin developed specially by Jim Dunlop; it's favoured for its combination of maximum memory, minimum wear and matte grip surface which means you can make these picks last a lot longer than others.
The chances are your favourite artists created their styles with TORTEX picks (unless Jim Dunlop has now made them a custom range instead!) including Slash, Gary Holt, Kerry King, Tony Iommi, John Frusciante, John Mayer, John Petrucci, Billie Joe Armstrong, etc... to name just a few.