Small testicles in an 11-year-old boy are usually due to developmental delays or testicular atrophy, among other reasons. There is no problem for an 11 year old boy to develop his testicles to 5ml or more. During adolescence, the balls will be relatively static, usually only 1-3ml, and after entering puberty, the balls will increase, and only at the age of about 17 or 18 will the balls reach the normal adult level, about 12-25ml, and it is usually considered normal for a male to have testicles of 12ml or more. If the testicular size of an 11-year-old boy is significantly lower than that of a normal child of the same age, and also not to the standard volume, he can go to the hospital to have his gonadal hormone level measured, and then determine whether treatment is needed to avoid affecting his reproductive function.