3.5 inch Springs - Trampoline Springs | TrampolinePartsandSupply.com
Upper Bounce Machrus Upper Bounce Mini Trampoline Replacement Jumping Mat, fits for 40 in. Round Frames, Using 34 3.5 in. springs UBMAT-40 - The Home Depot
5.5 Inch Trampoline Springs Heavy Duty Stainless Steel Replacement Springs, Set of 16, Recreational Trampolines - Amazon Canada