Thank you for viewing! This is a necklace made of surgical stainless steel (304). The clasp is a heart-shaped carabiner (a metal ring with an opening gate), making it easy to put on and take off without stress. Surgical stainless steels such as 316L, 304, and 202 are low-allergen materials and are used in medical tools like scalpels and scissors, as well as in luxury watches. They are special stainless steels with excellent properties, such as being rust-resistant and highly resistant to corrosion, oxidation, and heat. Sizes: Total length including clasp: 38cm (choker type) Total length including clasp: 43cm Total length including clasp: 48cm Please specify your desired size after purchase. If no size is specified, we will send the 43cm size. Thank you for your understanding. Chain: 4mm x 12mm Heart Carabiner: 17mm x 16mm Material: Surgical stainless steel (304) Color: Silver Please feel free to ask any questions.