Convertible headsets, also known as 3-in-1 headsets, offer all three main wearing styles (Over-The-Head, Over-The-Ear, Behind-The-Neck) in one and allow the user to switch styles as it suits them. There are also headsets that allow users to change from Monaural to Binaural wearing styles.
Make sure the build and method of converting the headset are of good quality. If you are likely to interchange the styles frequently the headset needs to be able to cope with the stress of the changes as well as every day use.
As with the majority of headsets, the weight is a major factor, do consider the weight of the headset for comfort purposes and how the headset fits when in Over-The-Ear wearing style and the noise cancelling benefits this could have.
Just like headsets with a single wearing style, convertible headsets can offer multiple connectivity options if this is what you require. Deskphone, PC and Bluetooth options are available from the majority of manufacturers.