Two weeks ago I needed to replace the temperature senor in the engine of my Saab 9-5. In the past I have always done this as part of a cooling system wide maintenance effort which included new thermostat, all new hoses, new coolant, etc. January in Michigan is no time to be laying on a cold concrete driveway draining coolant and the old sensor had completely failed. The only way to remove the sensor was with a 19mm socket s there is insufficient space to allow access for any of my assortment of 19mm wrenches that I used in the past. Unfortunately, the sensor has an electrical connector on the end and none of my sockets had a large enough internal recess to accommodate the connector. I went to see my neighbor two doors away who is a long retired Cummins diesel Mechanic and asked him if he had a 19mm socket that would work. He asked me to leave the sensor with him while he went searching through all his tool boxes. He sauntered back about 10 minutes later carrying the strangest looking wrench I had ever seen, and asked me if it would work. 3/4 inch size (equivalent to 19mm) with a deep offset to clear the intake system and other engine plumbing obstructions, and a 12 point box end. I looked at it and immediately said it just might work. He then told me it is the specialty designed wrench to allow tightening of the lock nuts on valve springs of Cummins Diesel engines, and that only the old times have these because the engine designs have changed. his was a Proto brand. It worked like a champ! I had the old sensor out and the new sensor installed in well under a minute. I lost less than a half cup of coolant that I immediately cleaned up with Kitty Litter and a broom. I returned the wrench then immediately went on-line looking for one of my own for future use as this neighbor will often vacation for a month at a time and he may not be at home next time I need to replace a sensor on another of my Saabs. I found a Cornwell brand version, with shipping, for under $25. A specialty Cummins wrench has been re-purposed as s specialty Saab wrench.