Etan Premium Quality Trampoline spring 180 mm set of 50. With this set, you give your trampoline its original jumping power back. These Etan Premium springs are 18 cm long and made of the best spring steel. So you can enjoy your trampoline for years to come. Before you replace the springs, measure the old springs just as well. This is done by removing a spring from the frame (make sure it is not a stretched spring) and measuring it from the end of the hook to the end of the hook.