Tampon size!!??

So I use Super+ and when my friends need tampons and I give them one of mine they say "I can't use those they are too big!" But honestly I thought the different sizes were for how heavy the flow is because I have Heeaaavy flow. But apparently it's for vagina size... but the tampon never hurts me like it does with my friends...?

Update: thank you guys for commenting. My friends are just being "drama queens" lmao and I was right, the bigger tampons are for heavy flow! Thanks!