The most common filament size is 1.75mm. This means the outer diameter of the filament is 1.75mm. (The less common size is 2.85mm, sometimes referred to as "3mm")
Bowden tubing has an inner diameter slightly larger than the diameter of the filament, so that it can fit through.
Before Capricorn came on the market, most Bowden tubes were made from pneumatic water-line tubing with an inner diameter of 2.0 to 2.1mm and outer diameter of 4.0mm.
For 1.75, our XS has an inner diameter of 1.9mm and an outer diameter of 4.0mm. Our TL, on the other hand, has an inner diameter of 2.0mm and an outer diameter of 4.0mm.
The second filament size is 2.85mm. For this size filament, both our XS and TL have a 3.2mm inner and 6.35mm outer diameter. This size is less common but is popular in Europe.
We offer two different series of tubing, available in two different sizes. Each of these are available in 1 meter (100 cm) and 2 meter lengths. We also have bundles with higher numbers of meters.
For most printers, about 30 to 40 cm of Bowden tubing is all that is needed. So a 1 meter piece of tubing is more than enough for most customers. You can use the extra for a second printer, or keep it as a replacement for when the first one eventually wears out.
We also offer a third size of tubing. This one comes in XS series only. It is a 2.0mm inner diameter, 3.0mm outer diameter. It is sold in small 10 cm pieces. This is called a "Heat Break Liner" and is used inside of some types of Hot Ends, inside the Heat Break.