Feature：
1. For stamped and machined parts, the main materials are: stainless steel, carbon steel, aluminum, nylon, etc
2. Glue injection groove with a certain depth (determined by the drawing)
3. Surface treatment includes spraying plastic, galvanizing, chrome plating, anodizing, etc
Function:
1. Store adhesive
2. Provide an interface to connect to the filter
3. Improve the end load strength of the filter element
4. Link between skeleton and filter material