Eggs usually refers to testicles, 1.5 years old baby testicles a large and small may be a normal phenomenon, may also be syringomyelia and inguinal hernia and other causes. 1. Normal phenomenon: normal bilateral testicle size, location can have some difference, if the size difference is not too obvious, then it is a normal phenomenon. 2. Syringomyelia: Syringomyelia is a cyst formed when the fluid accumulated in the syringomyelia cavity exceeds the normal amount. It can be manifested by the phenomenon of large and small testicles on both sides. 3. Inguinal hernia: because the sheath is not closed, the abdominal cavity of the omentum, intestines and other tissues into the scrotum, resulting in scrotal enlargement, which may lead to 1.5 year old baby testicles look a small one. When a 1 ½ year old baby’s testicles appear to be one big and one small, it is recommended that the patient go to the hospital in time for examination and standardized treatment according to their own condition.