Having been in the industry for 25 years, Boveda is a trusted and experienced brand in relative humidity control. But what does that even mean? Relative humidity (RH) refers to the percentage of humidity within an environment. In other words, it answers the question, 'how moist or dry is the air in my instrument case?' Boveda's founders and scientists discovered that the right RH has a huge impact on a wood instrument's performance & sound and safeguarding its construction. Using Boveda, you'll maintain a precise moisture level between 45 and 55% RH—no more mustiness in your instrument or bow case. Just slip a Boveda into a Mini Fabric Holder (available separately), position it in your case & forget about the pack until it starts to get hard. Once it does, just switch it out with a replacement pack. (Boveda 49 RH Size 8 comes in a pack of 10.) Each pack can last you up to 6 months. Its lifespan depends on how often you open your case, how airtight your case is, and how dry or humid the climate you live in is. Subscribe & Save to get Boveda replacement packs sent to you automatically. Proudly Made in the U.S.A.