Work on wooden walls, doors, windows, steel plates, and similar surfaces. Highly sensitive; adjust the o slowly and carefully to avoid discomfort to your ears. The o device operates by amplifying sound vibrations. When people speak inside a room, their voice creates vibrations that travel through surfaces and are captured and amplified by this device. Color: Black Material: Metal Package Contents: 1 x Detector 1 x USB Cable 1 x Circular Probe 1 x Needle Probe 1 x Headphone 1 x User Manual (English and Chinese) Note: The package includes only the items listed above. Other products are not included. Note: Lighting and display differences may cause slight color variations between the image and the actual item. Measurement error is +/- 1-3 cm.