1. The measurements are taken from the male threads at the outside edge. This ensures accuracy in determining the relevant dimensions. 2. Each item is sold individually. This allows customers to purchase exactly what they need without having to buy in bulk if not required. 3. The focus on male threads (outside edge) measurements means that the product's specifications are clearly defined in this regard. 4. Selling each item separately gives customers the flexibility to build their collection or use the product as per their specific requirements. 5. By basing the measurements on male threads (outside edge), the product's design and functionality are likely to be optimized for a particular purpose.