Complex sentence: The roll out mats are available in two sizes, one is 39'x 6' but the other is just 27'x 4' 6 and is designed to fit on a domestic patio or driveway.
Split into simpler sentences: The roll out mats are available in two sizes, 39'x 6' and 27'x 4' 6. The smaller mats are designed to fit on a domestic patio or driveway.