Kastar Tools serpentine belt wrenches release the tension on spring-loaded idler pulleys. Kastar Tools serpentine belt wrenches allow direct access to the tensioner without having to remove engine accessories or frame components. This can be done by rotating the drive end on the wrench to match the position of the serpentine belt tensioner.Ratcheting feature allows quick and easy positioning to access the tensioner from any angle. Heat-treated and nickel-chrome plated for strength, durability, appearance, and long tool life. Slim head design for access to restricted areas.