"Koni geltī emā?"

Translation: Do you have that helmet?

[evans.michael.p]

I am a tad confused as to how "koni geltī" is the singular "that helmet" and not the plural "those helmets."

[fp8LO0pf]

Why not 'Kona geltī emā?'
Shouldn't the question as put be translated into 'Do you have those helmets?'

[MadLatinist]

Gelte does not decline like ābra: geltī, with long i, is accusative plural and singular. But it has to be singular here, because koni does decline like ābra, and therefore koni can only be acc sing.

Tldr:

"Koni geltī emā?" = "Do you have that helmet?"

"Konī geltī emā?" = "Do you have those helmets?"