Tongda 3.5′ 3D Computerized Invisible Sock Knitting Machine. Multi-Size Compatibility: Supports 3.5, 3.75, 4, 4.5, and 5-inch cylinder diameters for diverse sock styles. High-Speed Efficiency: Running speed of 200-350 RPM significantly improves production efficiency and consistency. Complex Pattern Capability: Enables jacquard patterns, terry socks, and reinforced heels with 6-13 color interchangeability. Intelligent Material Saving: Reduces material waste through intelligent control systems and precise sewing trajectory calibration. Rapid Pattern Change: Optimized adjustments drastically reduce setup time for convenient pattern switching. Dual-Use Functionality: Supports both terry and plain sock knitting with single needle tube and dual entry design. Professional Manufacturer: Established in 1952 with 65+ years history, holding own International Trade Department. Comprehensive Certification: ISO9001, ISO14001, ISO13485 certified; products meet 3C and CE technical standards.