Octura 1/4-28 Threaded motor coupler for .078" (2mm) piano wire drive system. Used with Nitro Fuel Motors.Note: This coupler is for a NITRO Engine! Will not work with an electric motor!Fits motors 1/4-28 threaded shaft. Fits, solid piano wire diameter of .078" (2mm) Length: 1.3" (33mm)