Where is single rivets used for ?

They are used for pinning bridges onto lenses, pinning the temples onto lenses, mount universal hinges onto temples etc, anyway, as long as you want to mount two parts together.

Size: diameter from 0.8mm ,1.0mm,1.2mm,1.4mm, 1.6mm ;

Length: 2.0mm to 15mm or even longer;
Color: silver or gold ;

Material : nickel or soft stainless steel ;

Could it be customed ? what's MOQ ?
Yes, custom work is available as per your drawing, MOQ: 10,000 pieces.