I was concerned by the number of bad reviews, but given the low price, I was willing to risk it anyway.  Turned out to be a great decision. I use the iphone 4 quattro case and have been unable use most 3.5 mm phone plugs.  This adapter has a very slim body compared to others and fits securely in my iphone without removing the case.  I use a cassette adapter to pump the sound to my truck stereo and the sound is awesome!  I liked it so much and the price is so low that I just placed an order for three more so I have one in all my vehicles and travel kit.