As of July 3, the iRobot Roomba Plus 405 is on sale for $399.99. This deal saves you $400 on list price, and is the lowest-ever price according to camelcamelcamel. Our robot vacuum expert has hand-picked this deal as one of the best ahead of Prime Day.

Robot vacuums are incredibly useful, but tend to be expensive. Fortunately, I found some deep discounts leading up to Prime Day, coming up July 8-11 this year.

It’s rarely a case of which is better, more a case of what suits you best. Corded vacuums — a classic vacuum that plugs into the wall — provide more suction power, which means a more powerful clean, and have a larger capacity. That means they’re better for larger homes. They are, however, heavier and harder to lug around.