Capricorn is a manufacturer of high quality PTFE tubing for consumer grade and DIY 3D printers. Compared to cheaper brands, both TL and XS tubing reduce friction, and thus the residual effects of pressure buildup, in bowden systems for high speed printing. XS tubing provides a slightly lower friction coefficient along with tighter diameter tolerances for 1.75 mm filament, and thus is the recommended choice for higher quality filament brands. XS tubing is less translucent than TL, but allows for higher temperature filaments for hotends in which the tubing extends into the heater block (most Chinese designs do this).