OK. So I know this is a hard correlation to make, but from my personal experiences if a guy looks alot younger than his current age he almost always has a big dick. I don't have any experience with guys over 30, but for example if a guy is 25 but still looks like he is 19, he seems to almost always be bigger than average. Here are some personal experiences. Guy 1: Saw his dick senior year of high school, he was 17 but he looked no older than 14, always got made fun of in school for looking so young, rarely had to shave, no chest or hair anywhere on his stomach, very little leg/groin hair, young looking face. Finally got him to jerk off with me one winter break when my parents were out of town. Was expecting a smaller sized one since he looked so much younger. NOPE! He was at least 8 inches and THICK. Guy 2: 2nd year of college. Hooked up with this guy from my class who was 20 but he looked 16. Was fairly tall at 6 foot 1, but had very little body and facial hair, and still looked much younger than 20. He was 7 x 5. Guy 3: Senior year of college. He was 22 but looked 17. Was close to 7.5 inches. Yes he let me measure. haha Guy 4: He was 25 but looked no older than 20. Hung like a beast, 8 x 6. Guy 5: He was 27 but looked around 22. Was near 7 x 5.