...not trimmers as such - they are 'short stubble beard maintenance devices' that you can use anywhere as they need nothing else to work, are self-sharpening and have no disposable or consumable parts, and should last a lifetime. That said, like any hair product they require a technique, although you will not cut yourself if you do not know what you are doing it might pull. So our advice is to start with a clean-shaven face first and practice as the hair grows out to learn the technique without trouble. After learning you can progressively trim longer hair down also, but in summary the device maintains a 3-1mm (grade 0) stubble beard. There are full instructions, but people don't necessarily bother often so the above is the main points to know.