Ultra-Fab Products 21-001080 X-Large Ultra Chock and Lock Eliminates front to back motion by anchoring the opposing wheels of tandem axle trailers and fifth wheels; When engaged, the trailer wheels actually work against each other to arrest any created motion regardless of ground surface or slope One piece with easy to use lever; Can be locked to minimize theft (lock not included); Heavy gauge all steel construction with corrosion resistant zinc plating This XL Model collapses to 4.5" and expands to 10" 1 per box Manufactures Lifetime Warranty