I had a problem. I have a dock with a 30 pin connection, an iPhone 6 which takes the standard lightning connection and a case on my phone which didn't allow for a plastic converter as the hole was too small. I found this converter cable and as it is an Apple product, I knew I was getting quality. The short cable allows you to connect your iPhone to the dock and place it by the speaker. It charges the phone and you can listen to music whilst charging. Very useful at night to charge your phone and know that if you've set your alarm, it will wake you as you're battery is being charged. This would work for other Apple products which have the lightning connection.
A useful bit of kit which I wouldn't be without.