It works exactly as discribed! Just screw it onto the front of the SPARC and away you go! It is also easy to see through! However, it is made of shiny black plastic so it is light but it is mkore visible than the flat black finish of the SPARC itself. It's also $34 for a plastic circle.
Pros: Extremely easy to use!
Cons: A little too shiny.
This review was written in the old system and had content requirements that are different than reviews written today.