MONACO — Hekkie Budler cradled his world championship belts lovingly then turned and, without hesitation, made a confession.

“This one,” he said, pointing to a green-toned leather belt, “doesn’t actually stay up. I have to put it on my shoulder.”

Budler shrugged. So it goes for the littlest boxing champion in the world, a battler who has a title belt that falls off his hips like old sweatpants and shoes he bought in the children’s section and a baby face that people often mistake for a teenager’s.

But Budler, a sprightly South African, does not mind being small. To the contrary, it means people often underestimate him, whether it was an oversize rugby player in high school who tried to bully him (and got popped) or a boxing fan who thinks the tinier fighters don’t pack any punch. “There have actually been times I wished I was smaller,” he said.