ESTES COX CORP-Estes: Flying Model Rocket Kit. Estes offers model rocket kits in a variety of sizes, shapes, colors and skill levels. Enjoy the fun of building a model rocket and the excitement of launching it into the sky! This package contains one Crossfire ISX model kit. Skill level: 1. Length: 15.6 inches. Diameter: 0.98 inches. Estimated weight: 1.3 ounces. Estimated altitude: up to 1150 feet. Recovery: Parachute. Assembly required. Recommended for ages 10 and up, adult supervision under 12. Imported.