I got these coils for my speedcobra (they fit), but wasn't that satisfied with the result. If you're playing on really soft feet and with a lot of anklemovement this could be perfect for your style of playing, but I play with a lot of force and legmovement. The coils won't do much then, since the main work of bringing your pedal back / the foodplate back up is done by the springs on the machine itself. Couldn't really feel a difference with the cobra coil installed - even on the hardest setting/ some adjustments.
Again: Would recommend for really technical soft playstyles, but not for heavy hitters ;)