With the upgrading of the equipment manufacturing industry, domestic requirements for crowned tooth couplings in accuracy, reliability and service life keep rising. Comparing Japanese, American and European counterparts helps clarify technical routes, standard differences and selection logic for equipment matching. In Japan, gear and crowned tooth couplings mostly follow standards such as JIS B 1452, with representative manufacturers including Sumitomo Heavy Industries and NTN. Their products emphasize modular design and high consistency, and are mature in precision transmission. Compared with domestic GICL series, Japanese products have richer experience in tooth crowning, noise control and batch stability, but purchase price and lead time are usually higher. Crowning of the tooth tip directly affects contact stress distribution. Domestic makers widely use CNC machining for tooth-form accuracy, while foreign makers have deeper know-how in optimizing the crowning curve and suppressing edge contact, helping reduce local stress concentration and abnormal noise. In summary, domestic crowned tooth couplings already have the technical basis to replace imports; users can select reasonably based on duty, budget and lead time. We will keep sharing selection and maintenance essentials for the GICL series.