The HKS Super Fire Racing M525RE is an RE-type iridium spark plug with an NGK 10.5 equivalent heat range, designed specifically for rotary engines (Mazda 13B / RX-7 / RX-8). The RE design uses a straight platinum outer electrode tailored to the rotary combustion cycle for reliable ignition, paired with a 0.6 mm iridium center electrode. The very cold heat range suits high-boost and high-RPM rotary builds. Sold as a 10-pack (wholesale case); a typical rotary needs multiple plugs (leading/trailing per rotor).
| Product Line | Super Fire Racing M-Series (RE rotary) |
| Heat Range | NGK 10.5 equivalent |
| Seat / Type | RE type (rotary) |
| Thread | φ14 x 21.5 mm |
| Hex (Wrench) | 20.8 mm |
| Center Electrode | 0.6 mm iridium (straight platinum outer) |
| Application | Rotary engines (Mazda 13B / RX-7 / RX-8) |
| Quantity | 10 plugs (case) |
| Part Number | 50003-M525RE |
Shipping: In-stock orders placed before 3 PM EST ship the same day, and everything else ships within 24 hours. Standard, expedited, and overnight options are available at checkout. Backordered items ship as soon as we get them back in stock. Contact us for lead times. See the full Shipping Policy.
Returns: 30-day returns on new, unused items in original packaging. See the full Refund Policy.
