Material and Technology: The spring is made of high-quality galvanized steel, which is rust-proof, moisture-proof, and has high elasticity. It is more suitable for long distances and outdoor trampolines. Dimensions: 4.5 inches/116mm (length), 3 mm (wire diameter). Provide the most coils to ensure the elasticity of the spring. Hook end Treatment: The use of advanced equipment to create a perfect hook end bending arc, the spring can be more closely connected with the trampoline, more elastic and safer when you use the trampoline. Spring Appearance: Practice has proved that the spring with waist drum design is more elastic. Our original intention of designing the spring with waist drum design improves the tensile performance of the spring and is more durable. Spring Installation: Before purchasing the spring, please measure the length from the hook end to the hook end. In the installation, you can use the T-hook to complete your trampoline assembly more conveniently and quickly Satisfactory after-sales Service: If you have any problems with the spring you purchased, please contact us in time to ensure that you are 100% satisfied. If you are not satisfied, a full refund will be given.