The top of the holder will have a standard thread which will allow you to screw in a lens with the same thread type. The lens holder may also incorporate a Infra-Red Cut Off filter and is typically made of Black ABS Plastic or Black Anodised Diecast Aluminium. Being an inch in diameter they take up quite a bit of real estate but give a better result. The Lens will screw into your PCB mount thus ensure it has the same thread. You will be able to purchase lenses of different focal lengths, made of either glass or plastic.
Plastic are cheaper and typically of lower quality than multi element glass lenses.
Lens can also come housed in plastic or aluminium. Beware of inferior quality. There are a number of parameters associated with the lens. The Focal Length expressed in millimetres determines the field of view. A typical human perception is about 40 degrees, thus this is targeted as the normal view.