This is the Hard Chrome 4.0mm Turnbuckle Wrench from Muchmore Racing.

FEATURES: Hard chrome wrench with purple handle Fits common 4mm turnbuckles made by Lunsford, HPI, Hot Bodies and many more

INCLUDES: One 4.0mm Hard Chrome Turnbuckle Wrench

SPECS: Length: 77mm (3.03") Diameter of Handle: 7mm (0.28")  

BOX DIMENSIONS: 2.63" W. X .25" H. X 3.25" L. BOX WEIGHT: .02 LBS.