The iRobot Verro 300 is designed for use on gunite or concrete and features a powerful hydro-jet system that power washes the pool, deep cleaning pores, cracks and seams. The iRobot Verro 600 is ideal for vinyl, tile and fiberglass pool surfaces and features sturdy PVA brushes that scrub and clean the pool, while the powerful vacuum and self-contained filtration system picks up and traps debris and microscopic bacteria.