Best Bottom doubler option is perfect for heavy wetters or for a long nap or car ride. Consisting of 2 layers of super thirsty microfiber and made to fit with any Regular insert option of the same size. Snap in the Doubler option and snap a Regular insert of your choice on top! Best Bottom Doublers are almost identical to the Microfiber Overnight inserts. The only major difference is thickness. Less layers of microfiber result in a thinner insert, a less bulky diaper, and more mobile baby!