BrickLink - Part 73590c03a : LEGO Hose, Flexible 8.5L with Tabless Ends (Ends same color as Tube, ends not removable) [Hose] - BrickLink Reference Catalog
Lego compatible pneumatic tube
Tubes 45026 | LEGO® Education | Buy online at the Official LEGO® Shop US
LEGO PART 25214 Brick Round 1 x 1 diameter Tube with 90 Degree Elbow (2 x 2 x 1) and Axle Holes (Crossholes) at each end | Rebrickable - Build with LEGO
Lego 1x1 Brick Round Tube Column Pick Color Black Gray Trans Blue Yellow NEW X20 | eBay
LEGO part 751 - White Hose, Flexible 8.5L, Tube 7L at BrickScout