Replacing sponge end: Sponge end can be easily replaced when needed. We recommend replacing every 30 days. Grab sides of plug and pull to unsnap it. Lift old sponge and remove from clip on the back by sliding it down the brush handle. Tip: Wet new sponge prior to reattaching to handle. Attach new sponge by fitting one hole to clip on back of handle. Pull sponge down to line up hole until it snaps in place. Your bottle brush is now ready to use. Tip: This method can also be used to remove sponge and sterilize in the dishwasher. Allow sponge to dry naturally.