Vehicle accessories for semi-trailers and heavy haul transport include mechanical leaf spring suspension sets and heavy-duty air spring bellows to boost vehicle stability for long-distance and rough-terrain transportation. High-strength steel leaf springs and reinforced hangers form mechanical suspension that distributes loads evenly and lessens tire abrasion, compatible with flatbed, dump and lowbed haulers. Air spring bellows offer superior shock absorption, reliable vibration isolation and adjustable height control, mitigating structural fatigue and lengthening equipment service life. All parts adopt wear-resistant and anti-corrosion materials to withstand harsh mining, construction and highway environments and meet international production criteria. Custom sizes and load-bearing parameters are offered to match various heavy transport fleets around the world.