I bought mine from Lockwood ( http://www.lockwood-aviation.com ) Look for SKU: GAK2DC8 - want to check with them but that should be a complete kit with two 14 mm (spark plug size) probes. Current web listing is for $74 + s&h. Will need about a 12ft extension, I just made mine from twopair & put the reference junctions in the fresh air well. Padgett