This trampoline Frame Pad is for use on a 12ft Trampoline with 8.5 inch sized Springs. The Heavy Duty frame pad consists of a 12oz coated vinly top material with a polyethylene bottom lining. Please see the graphics to determine the correct size of your trampoline parts in order to ensure correct product choices from our website. Determine the size of your trampoline by measuring the diameter of the trampoline frame. Take the measurement from the outside edge of one toprail to the outside edge of the exact opposite toprail. Be sure to take two measurements in different locations to confirm your size. Please remember when measuring your springs to measure an unstretched or undamaged spring. Measure the complete spring from hook end to hook end.