This is the 12.5-15mm Servo Horn Drill Gauge from Futaba.
Provides pinpoint measurments for drilling mounting holes from the
center point of the servo horn.
FEATURES: Measures holes from the center point of a servo horn in half
millimeter increments (12.5,13, 13.5, 14, 14.5, and 15)
Transparent green, plastic construction
Brass inserts in each gauge hole protects the plastic from damage
INCLUDES: One drill gauge
REQUIRES: Nothing is required
SPECS: Diameter: 2.35" (60mm)
Thickness: .085" (2.15mm)
COMMENTS: There is also a gauge that will measure 9.5mm to 12mm, FUTM2401