Yellow Jacket 40821 is a Refrigeration system analyzer boot with the Yellow Jacket 40821 you get more information on refrigerant and software updates, display images and FAQs. The display reads in analog, digital or a combination of both, and monitors two pressures, two live temperatures, subcooling and superheat, and saturation temperatures (liquid and vapor) for 84 refrigerants. The new Yellow Jacket 40821 refrigeration system analyzer features a full color graphics display and color-coded diagnostics for intuitive, easy reading.