LIFETIME JEWELRYLIFETIME JEWELRY 5mm Round Ball Stud Earrings 24k Real Gold Plated for Women and Men

What is the type of backing for the earring (tension back or clutch back)?

Do these come in a 4mm size?

Are these balls solid metal? I have had an issue with the balls becoming dented after a while because they are so thin. Will these be more solid?

Cual es la medida de la bola?