Back in the 1960s, Speidel sold a stretchable metal bracelet called Twist-O-Flex, which was very popular, especially with divers, which allowed them to easily slip their watch over their wet-suited wrist
To compete, many companies (Rolex included) produced stretchable versions of their metal bracelets. Unfortunately, while a nice convenience, stretchable metal links tend to pinch skin & pull (arm) hair, making them some of the least comfortable bracelets ever made, which is why many companies (Rolex included) continued to sell non-stretchable versions of their metal bracelets long after production of the stretchable versions ceased.