Boveda is easy-to-use, maintenance-free humidity control for wood instruments—fretted, bowed and woodwinds. Using Boveda in an instrument case: Requires zero maintenance—no more filling messy hoses and snakes and wetting sponges Maintains an ideal relative humidity range for instruments—45-55% RH Prevents wide fluctuations in humidity that cause the wood to expand or shrink, and degrade its performance abilities This single refills: Directional Starter Kit for displaying and/or storing: Acoustic guitar Semi-hollow body guitar Hybrid electric or acoustic guitar Acoustic or electric bass guitar Ukulele Mandolin Any string instrument with a center sound hole or port Single Fabric Holder for storing: Violin Viola Clarinet