Only Adjustable Humidifier for Musical Instruments Plus Hygrometer (Black / Silver) - By Humistat USA Helps prevent cracking, warping, shrinking, sticking keys and pads of instruments Enhances tone and slows aging Refillable, reusable, low maintenance, unbreakable, never leaks water Adjustable humidifier for best results in changing weather conditions - including hygrometer to monitor results 2.50" length humidifier, 1.75" diameter hygrometer - easy installation inside instrument case