Prader orchidometer

Photo of a Prader orchidometer for measuring testicular size. On physical examination, the patient's testicular volume is estimated by palpation and comparison with the models on the orchidometer. Each of the beads is labeled with its volume, ranging from 1 to 25 mL. Prepubertal sizes are 1 to 3 mL, pubertal sizes are 4 to 12 mL, and adult sizes are 12 to 25 mL.