Sold individually, these fulcrum return springs are the correct size and tension for all Kahler fulcrum tremolos such as the 2500/2520 Traditional, 2710 Killer, 2720 Spyder, 2760 Steeler and all Original Floyd Rose (OFR) systems. Can also be used to upgrade the tension on any guitar with fulcrum style tremolo that uses a spring cavity and back plate like Stratocasters.
For fulcrum tremolos only. You may need up to 5 springs depending on your string set.
May be nickel plated as shown or anodized. Never mixed though. The spring tension is the same for either one.
All tremolo system springs should be changed every 3-5 years. Metal fatigue is the #1 reason for erratic tuning stability.