Camera Lens Protectors

Protects the part of the phone that projects furthest. Cheap relative to a camera repair. Usually sold in multipacks.

Can introduce flare or haze at night if the glass is poor. Badly fitted rings catch dust between glass and lens. Some interfere with macro focus.

Buy glass not film, and buy for the exact model, lens arrangements change every generation. If you shoot at night, test a few street-light shots before you commit: cheap lens glass shows its quality as flare around bright points.