P528 28 inch Plug-End Extension Spring is a Holmes spring replacement for heavier 1-piece/tilt-up/canopy-style garage doors. Two P528 springs - one on each side of the door - can handle a 105 pound to 175 pound door, with an initial tension of 165 pounds to 185 pounds Four P528 springs - two on each of the door - can handle a 200 pound - 350 pound door. Either 4 c-hook's or 4 w-hook's (sold separately) are required to connect the springs to the jamb hardware
2 x P528 springs support 105 pound to 175 pound garage doors
4 x P528 springs support 200 pound to 350 pound garage doors
Length over coils: 28 inch
Outside diameter: 1-5/8 inch
Wire gauge: 0.207 inch (no 5 wire)
Initial tension: 135 pounds - 145 pounds
Maximum allowable stretch: 22 inch
Manufacturer warranty: 1-year