Theyre useless. The FCC cracked down on these things a year or so ago and since then they are all forced to be within the specs, and well… Its not enough. Put the thing right next to a good antenna and you still get poor sound. But FM isnt exactly good to begin with anyways.
And its not $10, its $15. 50% more than stated 
Who really needs 3 of them anyways? But $5 each is a good deal.