Nylon cell window holder for use with 7894 photochemical cells and 7895 cell windows. The removable cell window is compressed between two FETFE o-rings for a leak-tight fit. Holder is then threaded into end of a 7894 cell until o-ring compression seal is formed between the holder and the cell. Supplied complete, consisting of threaded body, two FETFE o-rings, compression ring and four flathead screws. For replacement o-rings, see 7855-727, -729.