Many major construction machinery in China use a large number of oil cylinders. Many construction machinery manufacturers have their own cylinder factories:

Comparison: Xugong Hydraulic Components, Longgong Hydraulic Cylinder, Xiamen University Yin Hua, Samsung and Lianchangde all make hydraulic cylinders.

There are also many manufacturers specializing in oil cylinders: Jiangsu, Zhejiang and Shanghai, Guangzhou.

Contrast: Jiangsu Hengli Oil Cylinder, Guangzhou Shaoguan Weiguang, Changzhou Rexroth, Tianjin Pike, etc. I searched many manufacturers online, hoping to help.