Philips SPK9401W/93, Optical, USB Type-A, 3500 DPI, Grey, White Philips SPK9401W/93. Movement detection technology: Optical, Device interface: USB Type-A, Movement resolution: 3500 DPI, Buttons type: Pressed buttons, Buttons quantity: 8, Scroll type: Wheel. Illumination colour: Multi, Product colour: Grey, White