XCSOURCE 1.25" Extension Tube T Mount Adapter For Digital Camera Telescope Eyepiece DC636 Support split into sleeve + T word Ring. Conduct a comprehensive internal sleeve extinction treatment to prevent shooting light interference. T-Ring conducted a comprehensive internal extinction treatment to prevent shooting light interference. T-Ring using the M42 thread, supports direct connection SLR bayonet, conducted focus photography. Provides extra focuser back travel which is often needed for short-range terrestrial viewing or astrophotographic applications.