A small lead piece is connected to a thin wood plate with two springs. It may be placed outside the cello temporarily using the blue putty (provided) which will not harm the cello’s finish. It also allows for removal or change of position when conditions alter the wolf note’s presence. When permanent installation is required, it should be done using a titanium clamp with height-adjustable swivel pads. Resonators come in three frequency ranges: Low D-E, Medium Eb-F, High E-F#. Pictured are two resonators, one top and one side view.