Smalley L2 springs can be used as replacements for original Gamecube controller control stick (left) stickbox springs. Their force profile is a bit different, in my testing it's less tapered off, which allows for increased consistency with quick tilt inputs at the cost of dashing and similar quick full extension inputs taking a bit more force. My measurements, displayed as force-extension graphs, can be found here: Twitter post
In total, these L2 springs still feel very close to a brand new left stickbox spring, so if you like a stiff feeling with fast tight return, these are a good option.
Installing these into a stickbox is somewhat tricky, so buying these is recommended mainly if you already have experience with disassembling stickboxes.
You can see this visualized in the force diagram, which shows in-game input values (Melee levels) on the x-axis and force on the y-axis.
These are made from carbon steel, so they should not get wet, otherwise rust is a possibility.
