This is the Century Helicopters Universal Flybar Lock. FEATURES: Locks helicopter Flybars in place allowing easy pitch setting Works with 3mm or 4mm Flybars and 19mm-21mm tail boom sizes INCLUDES: Century Helicopters Universal Flybar Lock with Tail Boom Clamp, section of fuel tubing and instruction sheet REQUIRES: Installing between Tail Boom and Flybar SPECS: Length: .39" (10mm)