The rotors fit the Firefly or Micro Mosquito rc helicopters by Interactive Toy Concepts Ltd. It is good to keep a spare set of rotors on hand as a backup so you can keep flying, even after a crash. Includes: Rotor Set, Two Spacer Sets, Two C-clips, Two Foam Ballasts, Tail Fin and Sticker. Technical Information: 1 Upper and 1 Lower rotor, Diameter: 6.375 (162mm), Weight: 0.21oz (6g), Material: Plastic and Carbon Fiber. These rotor blades will only fit Firefly and Micro Mosquito RC Helicopters. Rotor Blade Replacement Instructions: 1) The rotors are held in place by a short rubber tube at the top of the main drive shaft. Pull gently to remove this tube. 2) Slide both rotors up and off, along with the plastic spacer that keeps the two rotors separated. 3) When replacing the rotors, first slide on the lower rotor (the one with the notched shaft on the bottom). 4) Next, slide the plastic spacer shaft over the rotor shaft. 5) Now slide on the upper rotor. The upper rotor is keyed to the D-shaped drive shaft and needs to be aligned in order to slide into place. This should not require any force to do when the parts are correctly oriented. 6) Lastly, reattach the rubber tube. NOTE: These rotor blades will NOT fit Bladerunner or Bladerunner Search and Rescue.