The retractable roof system is a closed cover side opening device installed on a dump truck (mud dump truck), which can effectively prevent various types of muck, sand, garbage, etc. from being leaked and thrown during transportation. It could reduce secondary pollution and damage to the urban environment during transportation. Cadro Company specializes in the folding open dump truck cover system designed for domestic and oversea vehicle conditions, road conditions and work habits. It is suitable for various kinds of slag, sand, mud, stone and cargo closed transportation for different occasions.