The hearing aid takes battery size 13. Some of the key features are: - Digital sound quality: the go pro hearing aids provide users with exceptional, crystal clear sound quality that is much cleaner, and crisper than the sound quality received with some analog hearing instruments. Automatic noise reduction: this feature helps to dampen the cumbersome sound of background noise in loud environments.With background noise selectively reduced, users can focus on what they want to, like conversations. This feature can also help reduce the mental fatigue that can occur over extended periods in loud environments. Directional program: the models of the go pro hearing aid feature a directional microphone that helps users pinpoint speech sounds in front of them, while reducing the sound from other directions. This can help further enhance the ease with which users can have conversations in noisy environments. All hearing aids I offer are unlocked for re-programming - including these units. Please, check with your local hearing aid professional if re-programming is needed. You must provide to me either a signed statement from a physician or a signed waiver before I will deliver this item to you. This item is in the category "Health & Beauty\Medical & Mobility\Daily Living Aids\Hearing Assistance\Hearing Aids". The seller is "insa_electronics" and is located in this country: BG. This item can be shipped to United States.