Tecomec Chainsaw high quality T-Wrench 3/4" (19mm) for spark plugs and 1/2" (13mm) for bar nuts. 

This wrench works on chain saw models like the Stihl E10, 009+, 010, 011, 015, 020 and more.

This wrench works on Efco models like the 940, 947, 952, 956, 952, 962, 970, 980, 981

The barrel length is 3" and the shaft length is 6-11/16"