If I have a Nikon Camera with lens 12-55ml, what cap do i need?

I see there are caps to protect the lenses with size 52 ml long and there's another sized 55 ml, so I don't know which one I need, I'm gonna order it online, please help!

Your lens is 12-55 millileters?

If you look at the front of the lens, you will see a number followed by the Ø symbol (such as 52Ø or 55Ø, etc.). That is your filter and cap size in millimeters (mm).

Lens 12-55ml… That, I'm almost positive, is meant to mean 18-55mm. That lens takes a 52mm lens cap.

12 to 55mm? Are you sure? Probably 18 to 55mm. Might tell you in the book, otherwise take the lens to a shop and get it fitted, probably a 52mm diameter. If you are so unsure about your lens best not to buy on line - a low-price item such as a lens cap is such a nuisance to have to return.