Black Menba 4mm OD 2mm ID 2 Meters PTFE Teflon Bowden Tube 1.75mm Filament For 3D Printer RepRap Rostock Kossel milk white Outside Diameter:4mm,Inside Diameter:2mm material: PTFE (Poly Tetra Fluoro Ethylene) Works great as a guide tube for CTC 3D Creator Fit for 3D Printer RepRap Rostock Kossel Package contents: 1 x 2 Meters PTFE/teflon tube