... 4. Excellent customer service Aluminum Extension Ladder 16 ft. Shanghai Yi Jing Mold Factory Our company specializes ... investment casting, injection molding. Usage of products: 16 ft. Aluminum Extension Ladder provides dependable, twist-proof performance. ... tester, Roundness Tester, Concentricity Tester, Height ruler, Depth ruler, Outside ruler, etc.Technicians self-check in productionEngineer spot ...