A lug is a protrusion on a watch case designed to secure the watch strap or bracelet.
Lugs are the protrusions extending from the watch case where the strap or bracelet attaches via spring bars. They define the watch's lug width (measured in millimeters: 18mm, 20mm, 22mm, etc.), which determines compatible strap sizes. Lug design significantly affects wearability and aesthetics.
Lug-to-lug distance measures from the top of one lug to the bottom of the opposite lug, indicating how far the watch extends vertically on your wrist. This measurement is often more important than case diameter for comfort—watches with lug-to-lug over 52mm may overhang smaller wrists.
No, lug width is fixed by the case design and cannot be altered without replacing the entire case. You must purchase straps matching your watch's lug width. Some watches use integrated bracelets where lugs and bracelet are one piece, making strap changes impossible or very limited.