Paraflex is a shock protection developed by Rolex in 2005. Paraflex differs from Duofix in that the spring extends fully across the balance staff jewel.
Rolex had long used the Kif Duofix anti-shock system, which was supplied by Parechoc. This common system was easy to install and effective in protecting the balance staff from breaking during sudden shocks. But the jewel could be dislodged completely in extreme shocks, because the wide U-shaped spring did not cover it completely. Duofix was also sourced from an external supplier, and Parechoc was experiencing corporate changes in the early 2000s.
In 2005, Rolex patented their own shock protection system. Paraflex used a reversible spring that spanned across the jewel and included a retainer around the circumference, providing better shock protection and keeping the jewel in place. This system was claimed to increase the shock resistance of Rolex movements by up to 50% over the Duofix system used previously. Additionally, the spring was reversible and symmetrical, reducing the likelihood of incorrect installation.
The first movement equipped with the Paraflex system was the low-production rectangular shaped Cal. 7040 fitted to the new Cellini Prince. This was also the first Rolex equipped with a display caseback, allowing the new shock protection to be viewed by the owner. And many 7040 movements featured guilloche patterns centered on the balance, emphasizing this new component. The Prince was produced in limited numbers, allowing Rolex manufacturing to come up to speed and test the new system in the real world.
Paraflex then spread to more high-volume models, starting with the Day-Date II Cal. 3156 in 2008 and the Explorer Cal. 3132 in 2011, and the Datejust II Cal. 3136 and Explorer II Cal. 3187 in 2012. By 2015, nearly every Rolex model included the Paraflex shock protection system and Parachrom hairspring, though the original Cellini Prince Cal. 7040 was dropped.