Only six months after iRobot launched its budget-friendly Essential robot vacuums, the lineup already has two new models. The Roomba Combo 2 Essential and Roomba Vac 2 Essential "double the cleaning power" of their predecessors and bring self-emptying dust bins to the series for the first time. The Roomba Combo 2 Essential ( 425) combines vacuuming and mopping capabilities, while the Vac 2 Essential ( 400) is a vacuuming-only model for those without tile or hardwood floors. Both have 100 percent stronger suction than the first Essential vacs. The latter already had 20 times the suction power of the Roomba 600 series it replaced on the low end of iRobot's product line.