Frederique Constant Slim Line

Most Frederique Constant Slim Line references take a 20 mm watch strap: 9 of 16. The lug width follows the case size: 25 mm case → 12 mm and 40 mm case → 20 mm.

Shop 18 mm Shop 20 mm

Frederique Constant Slim Line lug width by case size

16 references measured. Updated 2026-10-29.

Case	Lug width	References	Watch strap attachment	For example
25 mm	12 mm	6	—	FC-200MCS5B, FC-200MCS6B, FC-200WHDS5B
40 mm	20 mm · 18 mm on 1	10	—	FC-306G4S6, FC-306G4S6B, FC-306G4STZ9

References that take a different watch strap

FC-306V4STZ9: 18 mm, not the 20 mm of most 40 mm cases

Questions about the Frederique Constant Slim Line

Do all Frederique Constant Slim Line case sizes take the same watch strap?

No. The lug width changes with the case size: the 25 mm case takes 12 mm and the 40 mm case takes 20 mm. Check your case diameter before you buy.

Every Frederique Constant Slim Line reference

Other Frederique Constant families

Inside each one the lug width often changes: it is the reference that decides.

All Frederique Constant families → · Why the size changes inside a family →