Order an extra Boveda fabric holder to use with Boveda, the global leader in 2-way humidity control for wooden instruments. Double-sleeve saddlebag holds two (2) 49% RH Boveda Size 70 (sold separately) to precisely achieve and maintain between 45% and 55% RH—the safe zone for wood instruments. Drapes over strings and into the sound hole. For musicians who play multiple instruments, including acoustic guitars and basses; guitarróns; violoncellos; double basses; bass clarinets; and bassoons. Always use a protective leak-resistant Boveda Fabric Holder with Boveda (not included) for maintenance-free humidity control in an instrument case.