伯特利：通用汽车是公司的第三大客户

Group 1 - The core point of the article is that Bertly (603596) has identified General Motors as its third-largest customer and the largest customer for its lightweight product sales [1] Group 2 - Bertly's interaction with investors highlights the significance of General Motors in its customer portfolio [1] - The emphasis on lightweight products indicates a strategic focus on this segment within the automotive industry [1]