While you often do get a small screwdriver with many RDA’s it typically isn’t that good so quality screwdrivers are absolutely essential. All RDA’s are different and come with various sized screws, some are Philips's heads, others flat tops. Some are even hex screws and require an Allen key to tighten. A good set of screwdrivers will also typically have the diameter of them marked on the box. This is helpful and for the most part, you will be wrapping your coils around a 2mm or 3mm screwdriver.