Etan Premium Quality Trampoline spring 220 mm set of 10. A set of 10 Etan Premium quality springs, made in the Netherlands from the best spring steel. This steel contains zinc which makes it the most powerful springs available! Suitable to replace springs with a spring length of 22 cm. How do you measure the spring length? Remove an unstretched spring from the frame and measure from the end of the hook to the end of the hook. Are you in doubt? Please contact us. We will be happy to advise you.