This 15mm plastic intake manifold set is designed to fit almost any 2-stroke ATV, Dirt Bike, Pocket Bike, & Mini Quad up to 49cc. Also used for some 2-stroke scooters and smaller buggies/go-karts. Opening is 15.5mm and carburetor mounting holes are 3.1mm apart centre to centre. The mounting holes are 4mm and 3.5mm apart centre to centre respectively.