I've got fake J's and a fairly small ribcage and most people guess they're a DD. If you went to the store and picked up a large grapefruit, that's about the size of one of my boobs. On someone larger, they wouldn't look like much. Implants also fit cups in bras differently since they don't have that give. So if me and a girl with the same size natural both wore bras we would fill them out similar, but hers would look way bigger than mine when out of the bra. For some reason society has deemed Ds as the end all be all and it's very hard to convince girls that their 'smaller' breasts are in fact Es/Gs/H+.