When sourcing dolly trailers, the load capacity (Payload) is the most critical factor; ensure it matches your specific hauling needs, typically ranging from 10 to 50 tons for standard industrial models. Pay close attention to the axle configuration (single, tandem, or tridem) and the suspension system, where mechanical leaf springs offer durability for rough terrain while air suspension provides better shock absorption for fragile cargo. Additionally, verify the fifth wheel height and kingpin size (usually 2-inch or 3.5-inch) to ensure seamless compatibility with your existing tractor units and semi-trailers.