The original JDM steering wheel boss kit adapter brand HKB Sports! HKB Sports has been around since the 90s and have been manufacturing quality steering wheel hubs for all applications of JDM vehicles. Their steering wheel hubs, often called "boss kits" in Japan, feature a dual bolt pattern that can fit both MOMO/Sparco/OMP and Nardi/Personal steering wheels.
 
OR-18 fits 89-97 Miatas NON airbag (can be modified to fit airbag models)