This is the 5.5mm XT Adjustable Nut Driver from Tekno RC.

FEATURES: CNC machined weighted and balanced aluminum handle with knurling for comfort and sure grip CNC machined high carbon steel adjustable length 4mm shank tip Size of each tip laser etched for easy identification Large M5 set screw for securing tips firmly in place

INCLUDES: 5.5mm XT Adjustable Nut Driver  

BOX DIMENSIONS: 2.50" W. X .75" H. X 4.13" L. BOX WEIGHT: .12 LBS.