When I got these, I was really hoping they would smell strong and last once they burned like some of my other incence, but these really didn't have a smell to me. I am not sure if that is because all the scents are packaged together or if they are old, but was really hopeful on these being strong. They do work in my backflow burner and did seem to last the timeframe that they stated. My burner is black so didn't notice any coloration changes in it like some did. #RankBoosterReview