When lifting concrete it requires drilling holes in through the top of the concrete to get material underneath the slab to fill voids and lift concrete back to a desired height. With mud jacking or grout jacking, the holes are larger and require more holes to be drilled due to the material that is being injected. When using polyurethane foam it goes under the slab as a liquid then a chemical reaction occurs expanding and turning into high density foam. This product is able to travel further filling in larger voids and ultimately supporting the slab in a more effective way. When considering concrete lifting most people are looking to spend less, and also not change the looks of the concrete they have. Typical slabs only require 3 5/8″ holes. Two of those holes can be used to lift the concrete and control the pitch of the lift, and the third hole is typically drilled about 2 feet behind the other two and used to support the lifted slab, filling in any void. Landmark Lifting only uses the best products and believes whole heartedly that polyurethane foam is the very best product available to the public for concrete lifting.