Well my friend just bought a 93 Miata and the guy had a extra pair of HKS lowering springs so I was wondering would it fit my 99 NB?

 

Not if you have NB-style shocks.

On the NA, the lower spring perch is flat and the bottom of the spring is formed such that it will sit properly on a flat surface. IOW, the final turn of the coil is formed into a flat surface.

On the NB, the bottom of the spring is not contoured into a flat surface, it's just sort of chopped off. To match this, the lower spring perch has a contour which matches the bottom of the spring.

I'm having a dickens of a time finding a clear picture to illustrate this. Here's the best I can find:



See how the area upon which the spring rests is angled and unevenly shaped? Those are NB shocks.


Here's an NA shock:



Flat spring perch.


Ah, here we are. This is an NA spring. Note how the last coil on the bottom (right) is flattened out such that the end of the spring meets itself:





Here's an NB spring. The end is just hanging out there:





It's just as well. Those HKS springs are ****, and will ruin both your handling and your ride comfort. Far too low of a springrate for the length- the car winds up practically riding on the bumpstops.

 

Oh damn alright fasho thanks!