The springs themselves are made of high-quality galvanized steel, anti-rust, unbreakable, crack-resistant, excellent resilience and durability. Dimension: 5.5 inch (Total length including hooks), 3mm (Wire Diameter) Suitable for trampolines from 8ft-14ft.One end of the hook is curved at an angle that provides the superior hold. So, they are extremely safe. You can jump and bounce without the fear of the springs coming off. It is designed with a waist drum for bringing great bounce to your trampoline(wider diameter for more bounce), has better elasticity and stretching ability than those shaped straight, which will give you a better jumping experience.Unlike other cheap plastic trampoline spring pullers, our spring pulling tool is made completely of Stainless Steel and is in one piece, much more sturdy and comfortable to use, won't hurt your hand, makes assembling a trampoline much easier.