This is the JR Radio G3703D/DS3500G Gyro/Servo Combo Pack.Features:Wide application range from 450 electric to 90 size nitro helisAluminum case for crash damage protection and RF shieldingHeading lock and normal modes availableVery popular size for 450 and 500 size 3D helisJR's legendary digital holding power and resolutionProvides outstanding tail hold for aggressive 3D performance