Thermo Scientific Barnstead 09.4003 Smart2Pure pretreatment filter system. This filter system is compatible for use with Barnstead Smart2Pure, Barnstead LabTower TII, or Barnstead LabTower RO systems. This is compact with model numbers 50129869, 50129872, 50129870, 50129688, 50129873, 50129885, 50129874, 50129887, 50129888, 50129890, 50129889, 50129845, 50132193, 50132141, 50132394, 50132191, 50132196, 50132393, 50132390, 50132391, or 50132392. This filter is used when the quality of the feed water does not match the required water quality for your point of use water purification system. This includes the filter housing and one filter.