"Apple is most exposed," Neil Campling, co-head of global thematic group at Mirabaud Securities, told CNBC by phone Tuesday. Drilling into the numbers you can see why. In its last fiscal year, Apple generated nearly 20 percent of its revenues from Greater China, which equated to $44.7 billion. In 2017, it shipped over 41 million iPhones into China and was the fifth-largest player in the market, according to data from IDC. On top of that, it has around 40 stores in China.