Turtle Plastics Dura Crib Blocks interlock, stack, and provide a stable, secure base for any load. Each Dura Crib® block is labeled with a Working Load Limit (WLL) for clear safety guidance. Turtle Plastics Dura Crib® blocks are made in the U.S.A. from 100% recycled plastic with a reliable and repeatable formula for unmatched durability and strength providing a safer, cleaner alternative to traditional wood cribbing.