|The size given is the longest measured inside diameter of the slider. This inner diameter should be about 1 mm smaller in the slider/adjuster, as the width of the shoulder strap that is attached to your bra . With very thick shoulder strap ( as shirred bands ) , the inner diameter equal to or even 1mm larger.
If the diameter is significantly larger the shoulder strap can tilt the slide and lose its functionality . Slider will be used with wider shoulderstraps also in place of the ring , from sizes about 20mm .
If we can offer matching rings you will find them underneath.