The U-Tubes started life as a straightforward replacement part for the Hooptie, but we found them so useful we hand to make them their own product. For Families: U-Tubes are stronger and lighter than the RunningBoards (100 grams per side - about the average weight of a hamster). They also have great weather resistance, as they are made out of aluminum letting them shrug off the effects of sun, rain, and muddy boots. Speaking of mud, the twin tubes support feet but let debris or water fall through. For Cargo: U-Tubes have the same carrying capacity as Wideloaders but sit about 4.5" narrower per side so you can snake through tight spaces, as well as a clipped front corner improving foot clearance. They work great for smaller, dense cargo, like lead-acid batteries (sound bikers take note), bricks, and buckets of paint. Not compatible with the LongLoader.