An attribute provides you with various army attributes when you upgrade red equipment to LVL 45, 50, and 55.
To increase the enhancement, you can click on the equipment itself inside the factory, then click on the "enhancement" icon, then a window will appear showing "Equipment enhancement."
When equipment enhancement buildings reach level 5+ you will get:
Increase Tank attack power by 50%
Increase Artillery attack power by 50%
Increase Special vehicle attack power by 50%

When equipment enhancement buildings reach level 10+ you will get:
Weakens enemy assault cannon defense by 50%
Increase damage against enemy assault cannon by 100%

When equipment enhancement buildings reach level 15+ you will get:
Increase Tank attack power by 150%
Increase Artillery attack power by 150%
Increase Special vehicle attack power by 150%
Total marching troops +100,000.

Notes:
The max limit for equipment enhancement LVL 45 is 10+.
The max limit for equipment enhancement LVL 50 is 10+.
The max limit for equipment enhancement LVL 55 is 15+.