HOW BOVEDA WORKS FOR MUSICAL INSTRUMENTS: Boveda 49% RH protects wood instruments & their accessories by stabilizing the humidity within the ideal range-45-55% RH. If the air inside a case is too moist, Boveda absorbs that moisture. If it's too dry, Boveda releases small amounts of water vapor into the case. Wide humidity fluctuations will cause the wood to expand or shrink, which puts stress on the instrument & degrades its performance abilities. | CHOOSE BOVEDA: Boveda's the only patented 2-way humidity control solution with more than 25 years of experience. Using saltwater in our humidity packs, we provide the fastest, most precise humidity control in the market for wood instruments. When you invest in an instrument, you want to ensure you take care of it to produce optimal sound. Boveda is the only humidity solution that can do so within 24-48 hours. | HOW TO USE: Always insert a Boveda pack into the included protective Boveda Fabric Holder before using in an instrument case. Remove the Boveda from the plastic bag before using. DO NOT cut or open the brown humidity packet. Slip the packet into the holder. Place in case and close the lid. BOVEDA DOES THE REST. Replace every 3 months. NEVER MIX the 49% with any other %RH. | WHO IS THIS LARGE BOVEDA KIT FOR: Players of acoustic guitar; hollow-body guitar; nylon string guitar; semi-hollow body guitar; guitarrón hollow-body bass; cello/violoncello; double bass/upright bass; bass clarinet; or bassoon. Professional musicians; band & orchestra leaders; instrument techs; music teachers; hobbyists & student musicians use Boveda packs for easy & precise humidity management for instrument storage.