For manipulating the air fuel adjustment screw and tighten the lock nut without slippage when desired mercury vacuum level is reached. Alloy steel, 11" long. Fits both Mikuni and Keihin carburetors with 8mm hex nut and screw driver slot. Especially required for the GL1000! Eliminates fumbling with inadequate tools while trying to view your mercury manometer carb tuner, 08-010.