Good when your car does not have an integrated DAB antenna and you can easily use the existing one, e.g. the one built in the car body, as such. If you need a more powerful, active, DAB antenna, then a solution different to this adapter should be looked for, e.g. installing an active DAB antenna separately.
This means I don't have to install a DAB antenna. However, I can't say whether DAB reception is optimal with it because I don't have a comparison. The fact is that with DAB reception, there are often drop-outs that do not occur with FM reception: