what are small diameter industrial borescopes?

Small diameter industrial borescopes featured with:

• small diameter usually less than 3.9mm of the insertion tube of the industrial boresscopes.Such as diameter: 2.8mm,2.4mm,2.0mm,1.8mm or even 1.2mm with 2-way directions.
• It is a kind of industrial endoscope or inspection camera for  for the non-destructive testing of engines,gear box,pipeline etc.
• must be short tip of the probes less than 12mm ,it is for the hard-to-reach area of the inner spare parts or very narrow space. Vinex industrial borescopes with shortest tip less than 11mm can inspect small tube or pipeline easily.
• Must be firber optical lighting and better than led light sourcing.
• For inustrial use,it must be duable or wearable for the daily use.That insertion tube of the industrial borescopes are made with tungsten braied tube 4 layers.
• Also insertion tube must qualified with waterproof IP67 for inspecting liquid or oil or underwater. After use,please clean the lens with tissues.