The Chain CompanySterling Silver 16" 18" 20" 24" 28" 30" Inch 1.5mm Thick Italian Curb Chain Necklace

the chain length measured with it closed, like from neck down or measured with it open?

I need to know how wide the ring the clasp attaches to is at its largest point; I need to fit it through a piece of jewellery.

Does the seller provide return protection?

Hi, does it come with a certificate of authenticity?