The vertical speed indicator is a precision instrument which provides an accurate indication of rate of change of altitude. This instrument is temperature compensated and is provided with a zero adjustment screw on the face of the case in the seven oclock position. Power: Static system. Manufactured by United Instruments. Used in most production aircraft. Size: 3-1/8" x 3-1/8" x 4", Wt. 0.7 lb. TSO-C8b. Part numbers 10-00925, 10-00926, 10-00927, 10-00928 are LIGHTED VSI's.