Tein H-Tech lowering springs for Nissan 300ZX (Z32) are made from a material called "Vanadium" which results in a lighter spring and increases flexibility. 

The H-tech springs lower the ride height about half an inch.  The H-tech springs also have a slightly lower spring rate than the S-techs for a more comfortable ride.  Ride quality in sporting driving is still maintained by using the OEM bump rubber bump stops. 

Be sure to inspect and replace all worn out bushings and isolators found on your shock absorbers while installing the TEIN H-Tech springs. 
Complete your install with a 300ZX Nissan Shock Absorber Bushing Kit