When purchase co2 glass Laser tube for laser cutting & engraving machine, some customers do not know how to get a correct one. Even bought laser cutting/engraving and operated them before, but when they have to buy new one for exchange, some of user do not know how to buy same one or correct Laser tube 
There are more than thousands laser cutting/engraving machine supplier in the world, there is no a international standard to define a laser power. Even for same Laser tube, different supplier would call it in different power. For example for 60w-1250mm length/55mm diameter Laser tube, most of supplier call it 60w in real, but some supplier call it 65watt, 70watt, even 80watt. When customers buy a wrong Laser tube, maybe it cannot be installed to the machine because of different size, or maybe it cannot cut enough thickness material like before.
To help more and more customer choose correct Laser tube, I would like to share: We knew it deeply that if we define the diameter and length of Laser tube, then laser power will be defined at the same time during production. So that is easy way for customers to recognize the Laser tube by length and diameter. 
For example if we measure the length of Laser tube is 1250mm and the diameter is 55mm, then we will know the rated power for the Laser tube will be 60w, not others. If you do not want to know the exact laser power, just want to find a same tube with former one you have in your machine, then you just need to find the Laser tube with length & diameter same with yours.

Now we provide universal length & diameter for most of Laser tube installed in market for your reference, hope that will be useful for you to find correct Laser tube, correct laser power, correct size.

NOTE: Different manufacturer produces Laser tube with different peak power.  

1.     60w co2 Laser tube, length 1200mm, diameter 50mm
 
2.     80w co2 Laser tube, length 1600mm, diameter 60mm
              
3.     90w co2 Laser tube, length 1250mm, diameter 80mm
              
4.     100w co2 Laser tube, length 1450mm, diameter 80mm 
              
5.     130w co2 Laser tube, length 1650mm, diameter 80mm
               
6.     150w co2 Laser tube, length 1850mm, diameter 80mm