Identify the Landmarks of most Hearing Devices
Receiver In The Ear or Receiver in Canal devices are the most common form fitted today. Each model and manufacturer will differ slightly. Some will have custom made tips on the receiver (speaker) most will have a silicone dome. You will have a choice of standard disposable batteries or rechargeables. The program button and microphone ports differ according to model.
In The Ear or Custom Made 
Hearing Devices come in various sizes. The smallest have fewer or no controls, the larger styles can have twin microphones, volume and program buttons as well as a nylon filaments to help remove the instrument from the ear. There are different wax protection devices on the receiver outlets depending on size and manufacturer.
Behind the Ear devices usually have a standard size tube and an acrylic or silicone mould, however some smaller BTEs may look more like a RIC/RITE and have a dome fitting. The tubing is narrow bore and is ideal for ears prone to wax or infection. Some will have either program or volume control, some both and some neither. With standard tubing the mould can be removed for cleaning. The tubing should be replaced at least twice a year if not more often.