Rebuilding a classic Muncie 4-speed transmission (M20, M21, M22, or M23)? This set of bronze surface thrust washers is a critical part of the job. They're 1-inch in size and act as bearing surfaces between moving parts inside the gearbox, reducing friction and wear. Made from durable bronze, they're a direct replacement for worn-out originals. Using the right thrust washers is key to proper gear mesh and long transmission life. This unbranded set is brand new and essential for any proper Muncie rebuild. If you're doing the work yourself or supplying parts to your mechanic, don't skip these. Get your muscle car's transmission shifting smoothly and reliably again.