Herewith Kizuna Duratech D61 High quality badminton stringing overview; Kizuna Duratech D61 premium badminton string by ERR badminton restring Singapore. Kizuna D61 is simply launched in 2019. This Kizuna D61 badminton string as you can begin to see the gauge is thin only 0.61mm, but this string capable to provide “really hard” feeling.