Scope sheathing is the material that comes in contact with the product being inspected.
Rigid and semi-rigid scopes are almost always sheathed using 304 stainless steel tubing.
Flexible scopes have a wide range of sheathing options. Plastic sheathings include nylon 6, nylon 11, Teflon and polyimide. Reinforced sheathings can have nylon braid, stainless braid and tungsten braid on the outside or monocoil for crush resistance on the inside.
Illumination bundles are normally sheathed in squarelock stainless tubing with nylon or PVC extruded on the OD. MilliscopeII® illumination bundles are normally sheathed in a heavy wall nylon tube.