HiBy W4 Bluetooth Headphone Amplifier & Magnetic Backplate; Delivers moderate magnetic force, fits snugly to the phone back cover, and stays secure without slipping during daily use, walking or slight shaking.; Lightweight design without adding extra burden or much weight.; Slim and thin profile, does not bulk up the phone, comfortable to hold.; Easy to attach and detach, reusable and will not leave residue on your device.