allows use of 700mm tube in machine fitted with 635mm tube, I can manufacture in any length to fit any tube. (Please contact for pricing). this listing is for a 90mm extension with a fan and guard preinstalled in the cover. The fan does two things, the main purpose is to give a positive air flow along the tube in a direction, keeping smoke and fumes from entering the laser tubes optical lens area. This is a hard area to access for cleaning and often neglected during the cleaning process, causing excessive heat in the tube. reduced tube life and less emitted power.
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