Patazon Black Extension Dock Extender 30pin Adapter for iPod iPhone 4 4S
Bought 4 of these to attach to docks for iPhone 4 since my new case would not work without a dock extension.  Works fine.  Would have given a 5 star except -- comes off of the dock with the phone as opposed to staying on the dock and just removing the phone.  Can be a little annoying but otherwise works great.  The other thing stopping this from a 5 rating is the price.  Have seen them less expensive but I have Amazon Prime and this was the only one I found to have free shipping.  The others had additional 