The Bucket Adapter Replacement allows you to turn virtually any plastic bucket or container in a gravity water filter. Simply, drill a hole into the bucket, thread the Bucket Adapter through the hole, and attach the second o-ring and the female pre-filter end to the male end of the Bucket Adapter. Add a tube, hose clamp, and any MUV filters and you now have a gravity water filter. Perfect for large groups or survival situations.