Double-lumen extension tubes made from different types of plastics (PUR, PVC and PE) assessed in our study.

1) Octopus 2 ref. 841.264. 2) Octopus 2 ref. 5841.208. 3) Spider ref. PY2101NCM. 4) Smallbore ref. 011-MC33076. 5) Smallbore ref. 011-MC33077. 6) Smallbore ref. 011-MC33165. 7) MaxPlus Clear ref. MFX2502MP. 8) Edelvaiss CW2+.