Headache Free Turning Performance. The largest serial turner in the world, BACKHUS A75 turners are built for maximum capacity, extreme durability and intelligent operation. Regardless of your windrow width, the 6-series can accommodate it. Engineered with smart technology and innovative mechanics, the turner can almost run itself. Detailed feedback and control allows the operator to monitor all aspects of performance, while the electronic control systems automatically adjust to the compost to ensure the highest throughput possible.