The top is fully open without any cover, binding or filling spout, maximizing the opening area for unobstructed feeding and loading with extremely fast manual and mechanical filling speed. The wide flat mouth prevents material jamming, clogging and hanging, suitable for direct loading of large block materials. The fully reinforced sturdy bag has a stable load-bearing flat bottom, wear-resistant fabric and a simple structure with extremely low failure rate. Free of complex accessories, it is damage-resistant and easy to maintain, with convenient empty bag storage, high cost performance and strong practicability.