"Our factory manufacture various of carburetor"
Runtong is a Dellorto SHA "clone" carburetor (while usually marketed as a 'clone', some contend that the term 'clone' is insulting). It features a 15mm bore and a lever choke. The float bowl and top cap are both made of fairly low grade plastic. These can be found on eBay for as cheap as $23 as of 4/20/2016. It uses a single brass jet which is un-marked. The carb does not come with any air cleaner, or air box.
Recent Runtong carbs use normal Dellorto 5mm jets - the same kind that come with licensed Dellorto SHA's.
In general the seals are the weakest part of this carburetor. The banjo screen can be badly distorted from the factory and uses two flat rubber seals to fill the gaps, these seals will tear if the banjo is moved too many times, they may also crack on there own, so watch for leaks. Lastly, the rubber tip on the float needle may not hold up well under vibration and can wear quickly causing more fuel leaks.
Yes, you got what you paid for. But, you can make it work!