What is water weight bags for crane proof load test?

What is water weight bag for crane proof load test?

Water weight Proof Load Testing Bags are widely used forload test cranes, davits, derricks, winches, and virtually any other lifting equipment or load-bearing structure recognised as the most practical and safest load test solution worldwide.

20Ton water weight bag.
Dimension:3.5m diamteer, filled height 6meter.
Material: High performance PVC Coated fabric
Max load water weight: 20000KG/20ton
Accessary: Waterbag, inlet valve, outlet valve, repair kit.
Production type: High frequency welded for great air/water tightness.