Upper Basket Upper basket installs on the bottom of many Fleck, Clack, and Autotrol control valves to help prevent media getting pushed into plumbing due to pressure bursts and incorrect plumbing 1.05" Diameter Will fit most control valves (please check the diameter of your riser tube before purchasing to ensure that it will work) Twist-On Style The twist-on basket has tabs that lock into place when the basket is inserted and twisted. They are sometimes refered to as bayonet style baskets. Some older baskets only pushed in and don't have the tabs that allow it to be twisted and locked into place. The Top Distributor Basket is a twist on style for Fleck, Clack, and Autotrol valves that fits a standard riser tube of 1.05" diameter. This top distributor basket is designed to prevent any of the media from exiting your mineral tank.