Nylon cell window holder for use with 7894 photochemical cells and 7895 cell windows. Ace-Thred size #25. The removable cell window is compressed between (2) FETFE O-Rings for a leak-tight fit. The holder is then threaded into the end of a 7894 cell until O-Ring compression seal is formed between the holder and the cell. Supplied complete, consisting of threaded body, (2) FETFE O -Rings, compression ring and (4) flat-head screws. For replacement O -Rings, see 7855-727, -729.