Feature●Ultra-Fab Chock-N-Lock Deluxe Ultra Chocks for Tandem Axles●Enjoy greater comfort with Chock-N-Lock●Patented device locks in stability to eliminate front to back movement when youre in your RV●Locks the two wheels of the tandem trailer to render them motionless●Effective on most trailers regardless of wheel spacing or ground surfaceDescription Ultra Chock & Lock.