Magnets and gravity
The DongBang Spring Force Hand Needle Injector uses magnets at both ends to pick up needles and secure them in place. When at the insertion point, you can push the plunger to release the needle into its place with no effort at all.
This needle injector has a screw adjuster on top making needle depth a simple science. Turn the screw to set the needle depth you need and then move it into position. This is particularly useful for hand and foot acupuncture where an accurate and delicate touch is essential.