Only Adjustable Humidifier and Hygrometer Kit for Cellos, Basses and Bassoons (Brown / Gold) By HUMISTAT USA Helps prevent cracking, warping, shrinking, sticking keys and pads of instruments Enhances tone and slows aging - protects valuable Cellos, Basses & Bassoons Refillable, reusable, low maintenance, unbreakable, never leaks water Adjustable humidifier for best results in changing weather conditions - including hygrometer to monitor results 2.75" diameter humidifier, 1.75" diameter hygrometer - easy installation inside instrument case