Answer
CROS and BiCROS hearing aid systems are designed for those who have no aidable hearing in one ear and the better ear is either normal (CROS) or has a an aidable hearing loss (BiCROS). I wear a BiCROS system and find it very helpful even though, naturally, it cannot fully compensate for have only one usable ear. I would suggest that your friend makes an appointment at your local Amplifon Hearing Care Centre so that they can be given personalised advice.