Home theater – bought a system, and was wondering about wireless?

I bought a wireless home theater system awhile ago, and when I bought it, you could have bought an attachment to make it wireless. I decided against it because I was on a tight budget, and now I'd like to look into it, but I can't seem to find the attachment anywhere. Is there a standard attachment or is it specific to each model?

Note – I apologize in advance if my terminology is awful.
EDIT – ooops – I meant to say i bought a home theater system ago – you had to buy the wireless attachment separate.

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