I use to protect the front lens of my goal. I have already saved a goal with this type of product (device fell on the front of the lens, the filter was broken, but no trace of the objective lens). If in some conditions, the image may be slightly filtered, the protection side takes over (it hurts a scratch / impact on an object 800). The only complaint finish inside of the metal ring; pieces of fibers of the fabrics used to clean the filter lens remains somewhat hooked on this ring.
