4mm Entire unit is stainless steel which will not tarnish or fade. Perfect for everyday wear. Figaro necklace is approximately 18 inches, hardware adds 1 inch making 19 total inches. Note: Where the necklace sits on your breastbone depends on the circumference of the neck. Minimalist Boho Punk Goth Retro Tattoo Handmade Hoops Drops Dangles Crystal Cubic Zirconia Zircon Gold Silver Hand Crafted Costume Jewelry Fashion Jewelry Halloween