Bosch Double Iridium spark plugs are engineered for high-performance engines, specifically those using Gasoline Direct Injection (GDI). The "Double Iridium" designation refers to the use of a laser-welded iridium firing pin on the center electrode and an iridium inlay on the ground electrode.

Core Technology & Benefits:

• 4X Service Life: Designed to last up to 100,000 miles (approx. 160,000 km) compared to standard copper plugs.
• Double Iridium Construction: 0.6mm fine-wire firing pin provides superior ignitability, while the iridium ground inlay resists the high-heat wear common in turbocharged engines.
• 360° Continuous Laser Weld: Ensures the iridium tip remains secure under extreme combustion pressures.
• Nickel-Plated Shell: Rolled threads with nickel plating prevent corrosion and seizing in aluminum cylinder heads; no anti-seize is required during installation.
• Resistor Protected: Integrated metal-glass fused resistor suppresses RFI to protect sensitive engine electronics.

Part-Specific Descriptions:

1. VR7NII33X (The Asian-Market Specialist)
This plug is primarily designed for high-compression, modern Asian engines that require a wide gap for efficient lean-burn combustion.
• Primary Fitment: Toyota (Avanza, Corolla Altis, Vios), Mazda (SkyActiv-G engines in Mazda 3, 6, CX-5), and Nissan/Infiniti (V6/V8 engines).
• Defining Trait: Features a 1.1mm gap, specifically calibrated for the high energy requirements of Mazda SkyActiv and Toyota Dual VVT-i ignition systems.

2. YR7SII330U (The Honda/Hyundai High-Output Plug)
A heavy-duty plug designed for specific cylinder head geometries that require a slightly larger tool size despite the slim thread diameter.
• Primary Fitment: Honda (CR-V, HR-V, Civic), Hyundai (Tucson, Elantra), and Kia (Sorento, Soul).
• Defining Trait: Uses a 16mm (5/8") Hex size (unusual for M12 threads which usually use 14mm). It has an "S" projection (5.0mm) to reach deeper into the combustion chamber for a more centralized spark.

3. VR7MII33U (The Luxury V8 Performance Plug)
Engineered for high-stress, supercharged applications where heat management is the top priority.
• Primary Fitment: Jaguar (F-Type, XJ, XF V8 Supercharged) and Land Rover (Range Rover/Sport 5.0L Supercharged).
• Defining Trait: Features a shorter 3.0mm spark position. This "non-projected" style is critical for supercharged engines to prevent the electrode from becoming a "glow plug" under high boost, which would cause engine-destroying pre-ignition.