Wider fasteners such as the 57mm are preferred by many on more supportive bras, while the longer 2 hook man be used as front fastener on a Basque 

please note there may be a 1-2mm discrepancy in the measurement, this is not considered a fault as different manufacturing methods and different fabrics alter the finished product.  If the accuracy of the width is paramount, please email us and ask us to check the measurement before ordering