Our shackle bracelets have an rectangle shaped bar that makes the bracelet adjustable by either 0.5 cm (in the case of all the Istria and Trogir black bracelets and the 4mm Trogir bracelets) or 1 cm (in the case of all Adriatica, Dubrovnik and the 5mm Trogir bracelets). So basically each of our shackle bracelets have two sizes.
That is why, when you look at our product pages you will see, for instance, size M (16.5-17 cm) - that means the bracelet is made with a smaller(4mm) shackle (and with 4mm rope) that is adjustable by 0.5 cm. Or you can see size M (18-19 cm) - in which case the bracelet is made with the bigger shackle (and with the 5mm rope) and it is adjustable by 1 cm.
We can also make on special order bracelets for sizes smaller than 15 cm or larger than 20 cm - and you can contact us on email for such custom orders, but please double check and make sure you have the right measurements (measure the WRIST and not the length of a watch or another bracelet you own, please see the explanations above!!!), because we do not accept returns for these custom made sizes!