Below is an abbreviated Guide Tube Chart referencing which PT6 engines are an appropriate match for which guide tubes.  Not every Pratt & Whitney engine or guide tube is listed.  Only those common guide tubes we keep in stock.
These precision crafted, stainless steel guide tubes allow for the corkscrew maneuvering necessary to curl the flexible probe of our portable videoscopes for inspections into the most difficult areas of Pratt & Whitney PT6 engines. (Includes mount with stabilization screw.). The inner diameter of the guide tubers is 6.36mm. 
The most commonly used PWC borescope engine guide tubes are PWC34910-200, PWC34910-400 and PWC34910-600. ​
  • PWC34910-200 Curved Guide Tube appropriate for use in Pratt & Whitney engines PT6A-10 to PT6A-36 and PT6A-110 to PT6A-135A.
  • PWC34910-400 Curved Guide Tube appropriate for use in Pratt & Whitney engines PT6A-38 to PT6A-50.
  • PWC34910-600 Curved Guide Tube appropriate for use in Pratt & Whitney engines PT6A-60 to PT6A-67.
We have many videoscopes and borescopes can be fitted into these engine guide tubers for PWC engine hot section inspections.