319 Series Cooling System Test Kit - Car Kit 331900These unique patented design Cooling System Test kits feature expansion plugs with a tapering rubber cone to fit a variety of radiator and header tank neck diameters. With a range of just five plug sizes, it is possible to cover a very wide range of applications, from small cars to commercial vehicles & heavy plant. Temperature testing can be carried out by using the thermometer in conjunction with the appropriate expansion plug and by observing the