In short: the lugs are the two anchor points on either side of the Royal Pop 40mm's case, where the bracelet's pins click into place via the quick-release system.
The role of lugs in watchmaking
On a classic watch, lugs hold the spring bars that attach the bracelet. On the Royal Pop 40mm, they're designed to directly receive the quick-release mechanism built into Royal Pop Style bracelets.
Why their exact dimension matters
A poorly calibrated bracelet, with pins that don't precisely match the lugs, may click in poorly or come loose accidentally — hence the importance of a bracelet specifically designed for this model.
How to check your lugs' condition
Regularly inspect the lugs for any play or abnormal wear, especially if the bracelet's click-in becomes less firm than originally.
