YC 6FT Springfree no Gap Trampoline- Green W550P288198Bungees instead of metal springs, more soft and sensitive bouncing. (Much lower spring rate than metal springs, so the extension is faster .)Expanding with silence, very low noise, almost no. Patented elastic fixation structure, wearing resistance. Preferred Bungee rubber quality and outer warping strings,which can with stand 200,000 fatigue test. Safer than metal springs. Sometimes metal springs broke and burst out, it may hurt the user or people