Door forms include an polypropylene insert along with our standard form. The insert is reversible for either the left or right side. It prevents the concrete pier top from interfering with door installations. Made of resilient PVC. CPS forms are designed to fit on top of an 12” Sonotube. They can be reused if carefully removed or they can be merely used once and disposed of. No more building and staking forms for the pier. They save time and are simple to install with 4 screws (not included). Please see the ordering guide for more information.