The strongest, most secure sight glass elements available, Metaglas® mechanically prestressed windows, are available in a sanitary design for process applications. Unlike some other sight glasses, Metaglas sight glasses meet the USP Type 1 standard for pharmaceutical use. Described as offering the optics of glass and the strength of steel, these glass elements provide a level of safety, and a useful service life, well beyond that provided by conventional tempered glass or plastic in sanitary service. Even at the most extreme temperatures (as high as 536° F) or in overpressure situations, sudden, total failure - that involving leakage or explosive shattering of the glass - essentially never occurs. Also designed to be mounted in-line as a Sanitary Visual Flow Indicator and to accommodate Lumiglas Luminaires, such as the USL33 or USL35 style.