It rained on day when I was using my spoting scope at a match. It got mud and rain spots on the main lens. I carfully wiped down the lens with water and a lens cloth but had a lot of smuges and other spots on the lens I could not get off. The Leupold Lens Pen Cleaner took removed them easily.
Pros: easy to use, compact
This review was written in the old system and had content requirements that are different than reviews written today.