Scooter headsets are available in 4 main types which are threaded, standard threadless, semi-integrated and fully integrated.
The threaded headsets work with standard decks and are most commonly found on the entry level stunt scooters; typically these are available separately in stock colours which are black or silver. Threaded headsets cannot be used with threadless forks.
Standard Threadless Headsets
The standard threadless headsets work with standard decks and are generally found on some entry level scooters and most intermediate level scooters. They are available in a choice of colours and have a choice of loose ball or sealed bearings. Out of the two you will pay a little more for the sealed bearings but they are a lot easier to maintain and look after. Threadless headsets can also be used with threaded forks but a locking nut is required.
Semi-Integrated Threadless Headsets
The semi-integrated headsets are only compatible with a semi-integrated deck, a choice of colours for these is available but only a small handful of brands are available as these are the least used style of headsets in scooters. They will work with threaded forks but the locking nut is required for this.
Fully Integrated Threadless Headsets
The fully integrated headsets are generally found on some intermediate level stunt scooters and above, these are only compatible with integrated scooter decks and are always sealed bearings. Of the 4 main types these are bar far the easiest to look after and maintain. Like the other threadless headsets these can be used with threaded forks but a locking nut is required.