Clearwater CLE-11 RC-50/RS-50 Star 2001 Series Copper Cell works only on RC-50 and RS-50 model ionizers or with the CFL-39 complete flow cell assembly. The piece screws into the special black tee in the flow cell chamber section. The piece offers clear 360 degree viewing of electrodes for monitoring purposes. It's easy to unscrew with no tools or teflon tape required. Electrodes are 3" in length, 1 ¾" half-moon in diameter and includes O-Ring.