The product is a Detroit Diesel Engine 92 Series Service Repair Manual. It is compatible with tractors and specifically designed for Detroit Diesel equipment. The manual is focused on servicing and repairing engines in the Series 92 model. It is a comprehensive guide for maintaining and fixing this type of engine, with one unit included in the package. Price is per manual very readable. Nice condition 1984 revised edition make sure this is the right manual for your application.