The menthol crystals are pure menthol. Hard to describe unless you've used them before. Think Newport on steroids I guess. I use these a lot in many different juices to give them a little extra kick. My 'main vape' is a mint blend I mix up using Wintergreen, Peppermint, a few drops of Spearmint and Menthol Crystals. Sometimes a few drops of 'Koolada" for even more kick.
And yes, the menthol does do a good job of clearing your sinuses....LOL