There are two types of common headlight lenses, Glass and Plastic (Polycarbonate).
When a stone hits a Glass Headlight with reasonable force the damage is such that a hole though which moisture can penetrte is created. This is reason to fail your WOF/COF as the moisture will not only mist the reflector thus reducing light output but can also alter the beam causing glare to other road users. Novus apply a headlight skin which not only seals the hedlight but also protects against further damage.
Plastic lenses can become cludy and discoloured. This is due to oxidation caused by U.V. light and also reduces light output which can cause failure of WOF/COF. Novus can restore most lenses to like new condition.
NOVUS not only restores the Headlight to Like New condition but applies a unique coating to protect them.