StratoFins Screw-on Water Rocket Fins - Compatible With 2 Liter Bottles or Smaller Compatible with 95% of all available launchers either homemade or commercially available. Works with various styles: cable ties, rubber stopper, expanding tube, nozzle, or O-ring. No tools or glue required for assembly, simply screw-on to a 2 liter soda bottle or smaller. Take your water rocketry to the next level of higher flights with screw-on StratoFins. StratoFins kit includes 1 attachment ring and 3 fins along with an instruction sheet.