Your surgeon will decide whether over-the-muscle implants, which sit in front of the breast muscle and give a fuller breast shape, is right for you. There needs to be enough breast tissue to cover the implant, and so it is usually the option used with patients who have naturally larger breasts. In contrast, under-the-muscle implants sit behind the breast muscle to form a more natural breast shape, and this procedure is usually recommended for very slim women or those who have smaller frames and don’t have a lot of natural breast tissue.