The Problem with this O-Ring B61P-15-106A
The O-Ring supplied in most kits for the Thermostat Housing doesn't fit correctly. I ordered every part possible and found the best combination.
1999 Miata NB
Engine Coolant Thermostat Housing Gasket - Mazda (B61P-15-106A)
Thermostat Housing - Mazda (BPE8-15-170A)