3/16 welded steel construction with a no-nonsense design which fully encompasses coupler head of the Curt and some similar couplers. This “Plus” model is for more rare versions that are slightly taller in the area behind the ball socket area.  Accepts most all “puck” style locks (sold separately) which by design are completely bolt cutter proof. Time, noise, power tools or a cutting torch will be required to defeat our lock design which will eliminate most theft interest. We also sell a few different brands of the “puck” style locks with varying levels of security. Be sure to check out our installation video HERE. We offer discounts starting at 10 or more Ft. Knox Locks. If your coupler does not look EXACTLY like one of the couplers in the pictures contact us first before ordering for confirmation.  DO call us for clarification if you have any questions.   Made in America!