As the name suggests, it is shaped like a lobster, so it is called a lobster clasp. Generally made of alloy or copper. The colors are mainly gold, silver, and black. In daily life, many times will be used, such as necklaces, mobile phone chains, various ornaments, key rings and so on. Lobster clasps come in many shapes and different sizes. The industry terms are A09, A10, A11, A12, A13, A14, A15, A17, A19, A21, A25, A33, 45, etc. A09 is a model in the A series, with a length of 9mm, others can be deduced by analogy.