I have my first kilt on order. When I discuss it, it is always "the". When I have more than one I can start referring to them as "a".

But honestly, I have only heard "the" used to be generic. And is used for far more than just kilts... e.g. THE tuxedo is the accepted mode of formal attire in the U.S.

It's just a way of generalizing nouns into a group, as opposed to referring to specific objects. IMHO