These are the Tein H Tech lowering springs. These aprticular springs are specific for the 2015+ Subaru WRX/STI Sedan. The Tein H Techs were designed to improve both looks and handling. These were designed and tested in North America to be used with OEM or aftermarket shocks. 
Furthermore, these springs feature:
•    Chrome Vanadium construction
•    Progressive spring rate design
•    Gold powder coated finish
•    1-year manufactures defect and sag warranty which covers over 5mm sag, breakage, deformity, and noise. Does not cover powder coating and finish.