For those who say "Any HID "kit" you throw into the 99-00 Housing will suck and be a waste of money and blind everyone at night from all the glare," ANY bulbs that you install in your factory headlamp assembly WITHOUT adjusting or calibrating the beam will blind other drivers... As HID bulbs tend to have a wider range of illumination in some applications, it's usually common to aim them farther downward toward the ground to ensure that other motorists aren't being blinded by the brighter beam. Once properly calibrated, any HID kit that fits the proper bulb size for your car should work brilliantly without bothering others. If you don't know how to calibrate the beam... read up on that first, before purchasing a kit. As for the 1999 Miata, depending on what you're replacing (fog lights, head lights, brake lights, etc.), you and ANYONE with ANY car can find the right bulb types for your car by going to the Sylvania website:
http://www.sylvania.com/ConsumerProducts/AutomotiveLighting/LampReplacementGuide/