cd changer compatible?

[Herb]

Are all cd hu 6disk changer compatible? If not what should I look for.

[Mr Deagle]

For the factory radios? or aftermarket?

[Herb]

Sorry, let me clairify... Factory 6 disk CD changer compatable with Aftermarket HU. I have an e34 with all OE and want to upgrade to a indash cd player with mp3/aux input.