Inner horn NOT included. Purchase one of the following inner horns:
JR70721 - Adjustable metal Horn Inner V2
JR78036 - Adjustable metal Horn Inner V3
JR70712 - Adjustable metal Horn Inner V2 Futaba type
Ca distance from center to:
Hole 1: 10.7 mm
Hole 2: 13.5 mm
Hole 3: 16.7 mm
Hole 4: 19.5 mm