Red Hound Auto Premium Heavy Duty Trailer Wheel Chock. Built tough, this premium, rugged, quality Red Hound Auto Trailer Wheel Chock is factory tested and made from the highest quality industrial grade materials. Plus, the product is covered by a 1 year waranty! Quantity Included - One (1) Trailer Wheel Chock. Material - High-Density Polyethylene. Function - Large diameter doughnut shape prevents sinking and keeps trailer in place. Additional Info - Size: 6-1/4" OD 3" ID. High Impact - Large diameter donut shape prevents sinking and keeps trailer in place.