SkyBound Premium Zinc-Plated Trampoline Springs - Pack of 15 SkyBound Premium Zinc-Plated Trampoline Springs IMPORTANT: Prior to purchasing, measure your original springs from hook end to hook end, disconnected from your trampoline, and completely unstretched. For help, please contact SkyBound. SkyBound Trampoline Springs are designed to replace your trampoline's rusted, worn out, dangerous springs and return bounce to your old sagging mat. For more protection, consider SkyBound's Premium Gold Springs featuring yellow zinc plating to help ensure a longer life in humid/wet environments by helping to prevent premature rusting (oxidation).