LEGO part 99021 - Dark Bluish Gray Pneumatic Hose Connector with Axle Connector at BrickScout
Lego pneumatics - Wikipedia
Everything You Want To Know About LEGO Pneumatics - BrickNerd - All things LEGO and the LEGO fan community
Sheepo's Garage: Alternative parts for rare soft axles
Technic Parts, Pneumatic Kits With Pneumatic Pump Small V2 Building Blocks With Reinforced Cylinder, Air Pump Push Rod Switch Piston, Air Pipe Pneumatic Fittings Toy - Temu
32PC MOC Technical Pneumatic Hose Air Pump Push Rod Switch Piston Pneumatic Block Compatible With legoeds Pneumatic Parts
LEGO PART 5102c08 Hose, Pneumatic 4mm D. 8L / 6.4cm | Rebrickable - Build with LEGO
Lego® 4697b, 6104209 pneumatic hose, T piece, black
LEGO Technic Pneumatics - hose connector with axle connection
MOC Technical Parts 1 meters Pneumatic Tube Internal DIA 2mm External DIA 4mm Compatible with Lego for Kids Boys Toy 5102 21670 - AliExpress
Lego Technic Blue Pneumatic Hose 1 metre Length - Ideal Replacement | eBay
Bricker - Part LEGO - 5102c200 Hose, Pneumatic 4mm D. 200L / 160.0cm
Amazon.com: TEESE 21pcs Pneumatic-Kits Compatible with Lego-Technic-Parts, Piston-Pressure-Rod, Air-Pump-Cylinder-Hose, MOC Car Truck Replacement Parts : Toys & Games