It's fun to watch a baseball game, but did you ever wonder where the balls come from? Read on, and you'll find out.

In Dushan county of Guizhou province, more than 10,000 baseballs roll off the production line of a factory every day and are exported to Europe and the United States.

To make a professional-grade baseball, quality control is crucial. In the workshop of Dushan Runyang Sports Equipment Co, experienced operators strictly control the weight of each ball — between 142 and 147 grams.

"Customers have strict requirements for the weight of the ball. A small deviation can have a big influence on its trajectory and speed," said Wu Jili, a quality inspector at the company.

Geography makes Dushan an important link between inland Guizhou and major coastal ports in Guangdong province and Guangxi Zhuang autonomous region. Products can be transported to ports in one day.

The company started in 2003, taking advantage of the local government's favorable tax policies for outside investment.

According to Jiang Shaohong, the company's production director, the factory developed from a small workshop to a complete baseball production line that employs more than 200 people.

Shi Jinfen, an employee, said that she can earn more than 5,000 yuan ($791) per month during peak season.

In addition, stitching baseballs has become an important way for locals to increase their incomes. More than 3,000 people are engaged in this work at home.

Last year, the company produced 3.8 million baseballs, with an output value of 27 million yuan. At the beginning of this year, the company received orders for more than 5 million balls.

Zhao Yandi contributed to this story.