For reliability and durability reasons, E.I. will only manufacture ungrounded EGT probes. Ground noise at the engine can be a big problem for any piece of electronic equipment. Grounded probes transmit this noise back to the instrument. Grounded probes can also produce ground loops between the engine ground and the instrument ground. . E.I.s ungrounded probes eliminate the problems associated with gound noise and ground loops, providing a stable display and fast system response time. An engine analyzer MUST be coupled with a well-designed EGT probe to achieve excellence in the total analyzer/probe system. Military Bayonet type, 1/4 turn locking for quick removal. To be used with the A-101 adaptor. 700°F max.