Are you on a computer , or on a cell phone ? On a computer , click on Resources on the header . It will open up a page with everything from a file with the Library Index , to a range of charts on bushings/tube lengths by supplier or one with all pen types . A click on any of them gives access to a jpg file , which should open with another click .
Using a cell always makes things more complicated . Click on the 3 bars to the left of the Logo . Scroll down to Resources . Click on it and you get the Library Index . The arrow to the right keeps taking you deeper into the contents , starting with a whole bunch of files on tube length / bushings . A click on any one allows you to download the file or view directly by clicking on the jpg .
More or less , that should get you where you want to go .
There is an IAP app (costs $1) that has a searchable database of many pen kits, including tube lengths. You can run it on iPhone or Android.
It includes a "Drill Bit Converter" that converts inches (fractions), inches (decimal), mm, and drill gauges. That's useful, but what makes it outstanding is that it will show you the nearest fraction (to a /64th) and drill gauge along with the associated "error". The drill bit converter is worth the cost of the app by itself.
... for a buck ... take a chance ... Highly recommended!!