RO Reverse Osmosis 1/2" x 1/2" x 1/4" water feeding valve adapter RO Reverse Osmosis 2 Way Splitter (Water Feeding device), fit 1/4" tubing. fit most kitchen under sink plumbing, thread size 1/2". This will not work with pipes 1/2" OD or ID. has valve and outlet for 1/4" standard reverse osmosis tubing Installed on undersink valve with 1/2" thread. install onto plumbing without needs for drill