Boveda 49% RH Humidity Control Pack (2-pack) Made in USA This high-performance desiccant maintains a stable 49% humidity simply by placing it inside. Ideal for storing PSA-graded cards, unopened boxes of cards, and managing instruments like guitars and violins. No case required, making it easy to use and cost-effective due to its long lifespan. For long-term storage, replacement is recommended every six months. Thank you.