Rolex’s patented 5 mm bracelet extension system for Oyster bracelets is called Easylink.
Easylink is a compact comfort-extension link concealed beneath the clasp cover. The wearer can pull it out to lengthen the bracelet or fold it back to shorten it, usually without tools. Rolex developed it to accommodate normal wrist changes caused by heat, activity or swelling.
Easylink is different from Rolex’s Glidelock system. Glidelock provides a longer range of fine adjustment, especially for divers who may need to wear a watch over a wetsuit. Fliplock refers to a separate safety mechanism used on some diving-watch clasps, while Oysterlock is a clasp design intended to prevent accidental opening.
The approximately 5 mm adjustment is deliberately modest: it fine-tunes everyday comfort rather than replacing removable bracelet links or a full clasp-sizing procedure. Although associated with Oyster bracelets, Easylink also appears on some other Rolex configurations, so the exact bracelet and model matter.