Apple just sounded the alarm on a slowdown in China. Staying away from these 20 stocks could help you avoid the pain, Goldman Sachs says.

Apple China

Apple on Wednesday lowered its first-quarter revenue guidance, attributing a sales slump at least partially to a slowdown in China.
Shares were down more than 9% on Thursday.
The tech giant's warning indicates that companies with heavy exposure to China are facing headwinds.
Goldman Sachs previously identified 20 stocks that were particularly exposed to China.

Apple shares were under pressure Thursday after the tech giant lowered its first-quarter revenue guidance and blamed slumping iPhone sales on a slowdown in China.

"While we anticipated some challenges in key emerging markets, we did not foresee the magnitude of the economic deceleration, particularly in Greater China," CEO Tim Cook wrote in a letter after Wednesday's closing bell, sending Apple stock down more than 9%.

And it's not just Apple that is seeing weakness. The country's economic slowdown is visible in the data. During the third quarter, China's gross domestic product grew at its weakest pace in a decade. And in December, China's private-manufacturing sector contracted for the first time in 19 months.

The macroeconomic slowdown in China and Apple's sales weakness are due to many related factors, according to the SunTrust Robinson Humphrey analyst William Stein.

"These factors include: (1) US tariffs appear to be negatively impacting consumer confidence in China, (2) higher USD is likely denting demand in emerging economies, (3) competitive forces (both nationalistic and otherwise) from local vendors, particularly Huawei (private), may be triggering share loss away from AAPL, and (4) handset upgrade cycles may be slowing more than previously anticipated," he said in a note out to clients on Thursday.

While it's hard to determine which factor has had the biggest impact, most of them indicate companies with heavy exposure to China are facing headwinds.

Luckily for investors, Goldman Sachs maintains an index of US companies that get the largest percentage of their revenue from China. The firm has identified 20 companies it thinks will take the biggest hit in an environment unfavorable for trade between the US and China.

Here are the 20 companies Goldman listed, in order from sales least exposed to China to the most. (Goldman published the list in late October.)