Security Caps are machined from aircraft-grade aluminum. They are available in 1", 1-1/4" & 1-1/2" diameters to match StandOff Barrels. They can be tightened with an HD-SCT tightening pin which helps prevent removal without the tool.
There is also a 5/16-18 Thread 3/4" Diameter Security Cap that requires a hex key for tightening. It is designed for glass or plastics attachment. Both styles of Security Cap are available in standard Clear Satin Anodize or for additional cost, Black Anodized.