Interlocking Sides to provide stable lifting and/or support base 60 Ton working Load Limit 100 % Recycled Plastic - Made in USA Certified, tested, and tagged with working load limits Will not absorb fluids or rot like wood This Primo Super Stacker Cribbing Block from AME International has a solid, improved design with a hybrid profile that's ideal for use with heavy equipment, machinery and vehicles. Made of 100% recycled plastics, this durable block resists fuel, oil and most common industrial chemicals for longer wear and has a working load limit of 129,632 lbs.