Dampit Mini for 1/32 - 1/4 Violins (Also works for larger violins with petite F-Holes. We recommend using two in instruments larger than 1/4 size.)
Dampit says: Superior soft rubber sleeve encloses a special open cell sponge. Instructions and handy humidity gauge included. The Dampit humidifier provides long term humidity protection. It guards against cracking and warping. Helps maintain tuning and beautiful tone quality.