New design/style spigot mount 34mm throttle bore with 27mm venturi Tillotson carburetor. Outside diameter of spigot mount for hose/boot is approximately 43mm (1.70”).
This carb makes a great mild to modified big block OHV carb (390, 420, etc) and will also make a great open flathead carb. With its size and correct setup, its a killer 100-150cc 2-stroke carb. It would take a very highly modified small block to utilize the flow this carb delivers. 
**Please note that 32/28 valves are not considered highly modified anymore.