They are technically the same thing with the only possible difference being point of origin. China white has traditionally been slang for powder heroin from southeast Asia. #4 is referring to pure heroin and can refer to China white or powder heroin from SEA Afghanistan or Central America. The numerator of the #4 differentiates it from #3 heroin mostly found in Europe. #3 is heroin base and can't be injected without extra steps and is usually smoked. #4 is more highly processed and traditionally mainly found on the east coast and Midwest while the west coast was mostly black tar(which is its own thing). But even though China white traditionally referred to powder heroin it is now used interchangeably to refer to fent dope or other synthetic mix. Always make sure to clarify with your vendor about what the active ingredients of anything they offer as "China white". Hope that helps.