This is a great tool for adjusting turnbuckles. It's clamshell design opens up and clamps around MS21251 style barrels to hold them firmly in place as you rotate the knob. Two steel "holding" pins inside the tool positively engages the safety holes of the barrel and makes it impossible for the tool to slip. Very safe design will not damage turnbuckle while allowing maximum leverage. All-Aluminum design with steel holding pins. High quality anodized finish.