The need for commercial drivers has never been greater. Prepare yourself for success with Peterson's Master the Commercial Driver's License Exams study guide. This study guide not only breaks down each endorsement in detail but also offers multiple practice tests - 20 tests in total . You'll learn how to prepare for your exams and what to expect on test day with the following: Information about the written and skills exams Diagnostic tests to help you pinpoint your strengths and weaknesses Comprehensive review of material for all CDL endorsements and requirements: General Knowledge Air Brakes Combination Vehicles Double and Triple Trailers Tanker Vehicles Hazardous Materials Passenger Vehicles School Buses Practice tests with detailed answer explanations to help with every endorsement