It does what normal silicon ear plugs you find at a local Walmart or hardware store does. I mainly use it for swimming because my deep and small ear canal needs the extra silicon flaps to stay in but I still find that it sometimes slips out (not as bad as Ergo earplugs by Speedo) and I have to push it back in, which causes water to flow into my ear. Noise reduction works great in the pool if it's deep inside your ear. Overall, it's nothing overly special, go to Walmart and get a pair for $3 before you spend $10 on this.