Sika Pro Select Post Mix is a two-component, pre-proportioned polyurethane resin. It is mixed in the bag to produce expanding foam for supporting and backfilling fences, mailbox posts, gates, and signage posts. Suitable for all types of posts including wood, steel, and PVC. The lightweight pouch replaces two 50-pound bags of post mix. Mix-in-the-bag expanding foam for supporting non-structural posts so no water or special tools are needed. Sets in as fast as 3 minutes! (33-ounce bag).