1. Mounting hole diameter: 12mm / 0.47". 2. High flow air filter can reduce the resistance of the engine air intake and improve the air intake per unit time and volumetric efficiency when the engine is running. 3. Made of high quality material to ensure filtration efficiency. 4. Universal washable and reusable fittings for car air intake piping. 5. Greatly increase the power of the engine. Role of air filter: 1. During the engine to suck in a lot of air, the dust in the air is sucked into the cylinder, it will accelerate the piston assembly and cylinder wear. 2. Larger particles enter between the piston and the cylinder cause serious cylinder pull phenomenon, especially serious in dry sandy environment. 3. Air filter mounted in front of the intake manifold, it can filter dust, sand and ensure sufficient amount of sufficient air into the cylinder. Feature: 1. The air filter is a direct replacement for those that use an aftermarket intake system. 2. The filter will improve overall air