There is a vast variety available when it comes to looking for a hearing aid in the 21st century. Modern times have brought us hearing aids and types that utilize the upscale microprocessor technology. Hearing devices are so tiny that it is virtually impossible to tell if someone is wearing an in-ear hearing aid. There is another range of these devices that are small enough to be held on your fingertips. Let us look at some of the popular varieties of shell sizes that are available in the market today.