Westach Instruments are made of the finest materials especially for aircraft. TSO'd instruments are FAA approved per TSO-C43a, or TSO-C47. Westach has over 43 years experience in instrumentation. All Westach instruments have agate meter bearings, fully jeweled movements and rugged senders providing long life and top accuracy. Economical Engine Analysis. 2 1/4" instrument mount. Complete sets and spares in stock.