The M Line is perfect for an inground pool. Both the M400 and M600 can cover up to a 50 ft pool and they clean the waterline, walls, and floors. Both can run for up to 2.5 hours. Although the two are very similar, the M600 has a few features that the M400 does not. The M600 has 3 cleaning modes that include quick, standard, and enhanced. For more information contact either location.