This is a dome top fine tuner knob for all 2500 and 2520 "Traditional" fulcrum model tremolos. If you have a CAM system, you want the fine tuner for CAM systems. FYI: There are two types of fine tuners used on the "Traditional" models, either flat (6/32) or dome top (6/40). Inspect the fine tuner hole or your remaining tuners to see which one yours came with. This is the dome top fine tuner with 6/40 (fine) threading. You may need the flat top dome fine tuner with 6/32 coarse threading instead.
FYI: Just don't get confused... This fulcrum fine tuner looks just like a CAM fine tuner but the CAM fine tuner has a coarser, 6/32 thread, while this tuner has a finer, 6/40 thread.