4" x 4" x 18" Superstacker Cribbing Block, Black Certified and tested. Multiple sizes, shapes fit most applications. Interlocking or aggressive non slip surface. Non-conducting plastic resists oil and most chemicals. Does not splinter like wood. Carrying lanyards provided on all. Made from 100% recycled plastic. Rated up to 298,000 lbs (135,000 kg), depending upon configuration. Can be use with Lincoln log mating or pyramid mating 15210 No -