 Setting a fence post, a mailbox, deck footing, or even a small slab is quick and easy with Quickrete Fast-Setting Concrete Mix in the Red Bag. There's no mixing needed when setting posts. Just pour the dry mix into the hole and soak with water. Quickrete Fast-Setting Concrete in the Red Bag sets hard in 20 to 40 minutes. It's that quick and that easy. You'll find Quickrete Fast-Setting Concrete Mix at home improvement stores. Look for it in the Red Bag.