Crowned tooth couplings replace straight teeth with crowned teeth, distributing meshing contact more evenly along the tooth width and thereby improving load capacity and fatigue life. Domestic products follow GB/T crowned tooth coupling standards, differing from foreign products in structure and parameter systems. American gear couplings are based on AGMA standards; brands such as Falk, Lovejoy and Kop-Flex have deep influence in mining, energy and marine fields. AGMA products emphasize clear grading of rated torque and allowable speed, with structures biased toward durability and serviceability. Compared with domestic GICL, AGMA gear couplings offer richer choices in extra-high torque and special bore specifications. In materials and heat treatment, domestic products mainly use 42CrMo and 45 steel, carburized and quenched to a tooth-surface hardness of HRC58-62. High-end foreign products often use alloy carburizing steel with vacuum heat treatment, giving better hardness uniformity and delaying pitting and wear. 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.