Size 5 is the adult and U13+ match ball, while size 4 is for U8 to U12 players. Ordering the wrong size is the most common mistake we see from new buyers.
We carry both sizes in our footballs range from around $3.80 at MOQ 10. For a school or club we usually suggest roughly a 60/40 split between size 5 and size 4, adjusted to your age groups.
Tell us the ages you are buying for on WhatsApp and we will recommend the split.