Fudan Wingsoft Ltd. developed a product Line of Wingsoft Financial Management Systems (WFMS-PL) providing web-based financial services for employees and students at universities in China. The company used a wide range of variation mechanisms such as conditional compilation and configuration files to manage WFMS variant features. We studied this existing product line and found that most variant features had fine-grained impact on product line components. Our study also showed that different variation mechanisms had different, often complementary, strengths and weaknesses, and their choice should be mainly driven by the granularity and scope of feature impact on product line components. We hope our report will help companies evaluate and select variation mechanisms when moving towards the product line approach.